OGXcom had it isn’t it? or is it a piratez feature? (I remember jungle tiles for that)
Another thing that it’s in piratez are the extreme cold, the extreme hot and ¿toxic? missions, I hate them but I like them, you know what I mean ; )
I at least expect original Xcom mechanics where simply some units had more AP and melee attack only and where you needed to go around the obstacles. Smoke could decrease accuracy, exploded terrain movement and that would be about it. Anything other, while realistic, would likely unnecessarily complex the engine and move requirements even higher.
Movement mechanics are likely to have zero effect on today’s requirements. The big thing in regards to engine and system requirements is going to be graphics and destructible environments. As this is a turn-based game you can get away with lower requirements compared to a real-time game since there’s far fewer things happening simultaneously compared to a real-time game (for example DOOM 4 is limited to something like only 16 enemies active at any one time because of how more can quickly bog down the game).
I mean even the OGs had different movement costs based on the terrain type and direction of movement (going up/down was 8, diagonal was 6, tall grass was x1.5, etc). We already know that the game is using a TU system under the hood with the lines merely showing how far those remaining TUs will let us move. Given that tiles already store things like damage resistance, damage taken, and next displayed tile upon taking X damage, it wouldn’t be hard at all for them to have the tile also hold a TU value for moving through it, and again since it’s a TBS this on-the-fly calculation would have no discernible affect on system requirements. Hell they might already have the tiles holding the TU cost.
Most games implement something like that, right now I’m remembering Fire Emblem, rain makes units move slower, mountains are impossible for certain units, water is possible only for a couple of them, night empairs vision, so on. 100% sure Phoenix Point will do the same.