First of, I know that this is just pre-alpha yet and a lot can change, that’s exactly the reason I’m writing here. Lets see a few points:
-the biggest letdown in xcom, i mean the firaxis kind of xcom, is the progression. there are 2 kind of players, one plays for killing aliens, winning fights, completing tasks, the other plays for the progression. when you get to the top, its done, the game stops to be interesting (yeah, xcom games became boring rather quickly, after 10 battles i usually had all the important tech and a squad that can take on any mission).
i dont know much of pp progression yet but one thing is inevitable, due to the classes there will be a limited range of progression a toon can take. there will be no adapting to new enemies and new situations (sadly in this i see there will be no really new situations, slow adaption and light changes arent what im talking about). you will get a class, you will have probably a class fixed tree like in xcom and you get penalised for using anything else. imo this is a mistake.
there was an other game, ufo afterlight that solved this a lot better. there were only skills you can improve and those skills made a toon to have a class, i still had snipers, heavies and assaults, they just didnt have that marked anywhere. i knew what they are and the penalty for using other types of weapons came form the lack of skills. sadly the skills didnt come from doing things but were freely distributable but it was a lot more interesting and when through the game ive met different enemies i was able to adapt and train my heavies as close combat martial artists, my snipers as scouts etc because, yeah, in ufo al there were very very distinctive enemies (especially when martians came into the game or attacking the mindcontrolling base, first needed close combatant the second needed a full robot army).
Give freedom to the player and let us decide what weapons we want to give to a soldier and how we want to use them. And I don’t try to say by any chance to stop copying xcom and start copying ufo al, that game wasnt perfect either, doing your own version that is better than both of these would be the right choice;
how then? change the skills by the use of weapons and trainings. have training facilities to train strength, aiming, fitness etc, give minuscule skill for every day spent on training, it wouldnt make a soldier a superhero but would give a definite advantage over the course of the game. then have combat experience you get for using weapons and techs in battles and you could bring in things like painresistance for those get lots of injury but always survive 
just an idea, he could die slower for bleeding. and finally have schools where the soldiers can get different level of training that would give a distinct advantage in one weaponclass but would make them unavailable for a long time. This could be an interesting system and not even that difficult to make it up.
-destructible cover: this is one horrible invention xcom had and as i see you intend to follow them. when a single shot can destroy buildings/wall/military metal crate etc or the queen that can walk through literally anything. c’mon, human buildings are made to withstand natural catastrophes. there is nothing more to say about this. there should be strict levels of what can destroy what. like no sniper gun should destroy a concrete wall or a metal crate, it’s shell might passes through but thats it. walls shouldnt be brought down even by grenades, maybe c4 that should be available with training to open up walls and attack the back of the enemies but simply levelling the map is silly. Even the boss’s terrain destructionmodel is an xcom copy, straight from the sectopod…
-aiming mechanisms: the points you should look for:
1: accuracy of the weapons. while its static for any given weapon and really can be a cone like in your game, its not enough to model aiming
2: movement. sure in a turn based game the enemy is always standing in front of you but really they are moving/running when not in cover or shooting
3: accuracy of the soldier. aiming with a weapon is not as simple as pointing at the enemy and let a bullet go and let the random spreading of a gun decide weather it hits or not. every weapon makes it easier or harder to aim for the user at different distances.
like a pistol can have the same or better accuracy then an assault riffle on the same distance, still aiming with a pistol at 200 meters is mastermarksmenship while with an assault riffle anybody can do it. in the meantime aiming with a high magnification sniper riffle at an enemy in front of you is nearly impossible especially if the target is on the move.
4: stabilisation. aiming VERY heavily should depend on what position you take. crouching and proning should be accounted for and so should be manual, not some automatic crap that tells you what you HAVE TO do.
5: snapshot/aimed shot/burst fire/autoshot. they are there and could add to the game, the more options are the better, especially if you dont have to work much to implement them. they should just be different shots with different accuracy patterns and different tu cost again to just give the player more options.
As I see there are very few games accounting for these and pp is not one of them
also, as i see recoil is nonexistent in the game that could bring with a tiny easy change a lot extra gameplay like inventing things that helps with recoil, training your heavies strength to deal with recoil or taking longer time (using more TU for a repeat shot) for weaker units to deal with it… shooting could be interesting in an rpg too not only in an fps game…
imo accuracy should be heavily penalised as long as you are not right in the face of your enemy or have extreme tech level. no, dont give me chances, lover or higher, doesnt matter, give me accuracy or penalise accuracy based on actions, positions, weapons etc. we are not in a duckshooting range, we are fighting moving living enemies. pointshooting them for hp blocks… well, please, leave that for jake…
-movement: yeah, why on earth are you copying xcom? to make it boring already when pp gets released? do you want people to boot it up and feel like they have already played it to death? not a good start. do you know why games are being forgotten? because people gets familiar with them. when they already start familiar they will get bored even quicker, though now that you changed from the original idea of shooting will end your turn its still not perfect, it gives way too few actions, probably because of the small maps its necessary but you wouldnt have to have all these overcomplicated xcom maps. trying to fit more into less space is not necessarily good.
-hud: there are way too much information and way too few options. I dont want to see how many hp-s can i take or if i will disable of make him bleed, these should come from no chance but proper hitboxes with vital parts. I get that casual players might want this info but please remove them at least on higher difficulties. no circles, no damage previews, no hp bars. there should only be wounded/disabled/bleeding or dead
-and here it comes, HP/damage model, as noted above this having a number of hp-s and a far lower amount of damage potential only shows one thing… you have no idea how to make a combat interesting and first of all lasting. instead of variations you make one enemy to count 2-3 times or even 20 times. again, its probably the outcome or stuffed small maps where there are no real distances to have 30 enemies spread out, you have to make 5 enemies to last 30 shots. instead there should be a hitbox model, hit something wound something, if its vital part kill it, if not disable or wound it.
-armor: again just xcom copy. why? do you guys not have your own ideas? no, armor never worked like taking up some of the damage. it either saves you or not. if it bounces a bullet you are good if not you are fkd. and for this reason there should be the ap and he shells and maybe the hp shells for extended wound or limb damage but worse penetration. also the heavier/bulkier the armor it should penalise aiming or simply make it impossible to use some weapons with it (instead give special weaponry like heavy pistol heavy machine gun heavy sniper that can only be used by strong toons or in assisted armors)
-overwatch: such a far-fetched idea… willpower does not give you extra time, saved up tu-s do and thats not something you switch on or off, having just reactionshots for nothing… ohh c’mon. i dont like to talk about realistic things in fantasy games but here LOGIC is being defied. reactionshots should depend on spotting and available tu-s. someone leaves the cover and you have tu, decide if the toon has enough agility to take a shot on him and if yes take the shot…, tu-s over? thats it, no more shooting. you are slower than the enemy, you are fkd
-will: instead of giving you magic time, will should serve once the panic effect and also should contribute to aiming. its difficult to shoot with shaking hands but again, you shouldnt just copy xcom. panic is not all about hunkering down and losing the turn. it should come in rushing out taking random shots, like a maniac, or refusing to move when you want to send it out to an other position, fear from a specific enemy etc. for now, and this is the problem with xcom too, its way too calculable. its like playing math instead of an alienshooter.
-heavens: an other copy paste element… aliens raid a heaven go to save them. i hope it will all be on fire and helpless hobos will be running around as free target to the enemy… seriously. heavens are heavens for a reason and they can still be there in the wasteland because they are protected, hard to find and take on… instead of such silly xcom copy you could use them many different ways
1: help their raids, do joint missions in their areas, make them stronger and more advanced with it
1.5: build fortresses and man with your own soldiers to defend them in case of an attack
2: trade with them
3: hire soldiers from their ranks
3.5: convince them to side you
4: store soldiers and/or items/vehicles there
5: make them do works for you. manufacturing/building/researching
6: of course saving them can still be an option but shouldnt be built on it like xcom did
-base building, please do it right and make the built bases available as maps for home defense battles aka properly modeled rooms and hangers that looks on the tactical map just like on the base view. please. you build so many maps, this isnt difficult.
Thats it for now. Sadly Im aware that most if not all of this will be ignored, i wasted my time on it with good will…
Clear rules and limitations can make game more enjoyable. FiraXCOM did too much in this matter, but game after some modifications was still fun to play. 
At least it sounds like that in your original post. 
Yeah sure Mr obvious.