Different people have different levels of skill. Whats challenging to some is easy for others. The devs also have to take this into consideration.
Fact that a player has plenty of options just means that theres alot of tactical options for the player to choose from. You add nothing to the game and only take away if you reduce that number of tactical options.
Think the game is to easy, even on the highest tactical option? Well guess the game is just to easy for you or something. Some players then install mods for more challenge or look for other games for that challenge. Ive never heard of people asking for the devs to take away options to get more challenge though, that just seems weird to me.
Second wave options though I always apllaud. Those are overall generally always a good idea. XCOM enemy unkown did this very nicely and XCOM 2 had some as well (though dident do it as good as enemy unknown in my opinion) that greatly exemplify this. Want all your rookies to have random stats? Well you can! Want flanking to a gradual thing rather then a yes or no thing? You can! Want your resources to expire? You can get that! So much options. Can make life as challenging for yourself as you want, alongside the difficulty option.
Those changes arent intrussive though and dont alter the game for everyone who play it, just the ones that want that option specificly. Would add options to the player rather then take away and add to the replay value of the game.
Add this as an second wave option and im all game, just dont alter it for everyone.