Got through my first couple runs so far, I like it! (big fan of mech games myself)
I noticed the keybinding system doesn't seem to work past the first page (at least via keyboard access, since I can't use the mouse)--the reference letters don't move down to new options while scrolling, which I'm thinking was probably the intent (I had wanted to rebind the wait/skip key, but it was down further).
Really liked the innovative alpha-based target selection, haven't seen that one before, although I do wonder how the letters are chosen since it seems kinda random. Would've thought that the first or only enemy in view would simply be 'a' and go from there. (I realize that enemies you've seen before would want to retain the same letter, although probably no need to assign them letters until you've seen them?)
I like the noise system, knowing where enemies are (and enemies knowing about you) based specifically on the amount of sound made during movement and shooting. Fun how you can't generally hear infantry and this plus the louder enemies sometimes mixes things up in terms of optimal tactics.
Already decent atmosphere here running around a city (and destructible terrain!), though would of course be nice to see more development adding things like enemies with better weapons worth upgrading to. Good sound effects would go a long way, and ambient audio... man this is making me want to make a game like this again xD
Obviously endless other possibilities, but as is it's a 7DRL so can't expect to have all that, what's here is already pretty solid. Nice job! Planning on doing much more with it?