Environmental effects is a great idea, Aulex.
Imagine if a player has a SMD and you don't want to risk using your nuke right on the base. There is a mountain behind the player. You could fire the nuke and create a MASSIVE rock slide that falls onto an opponent's territory.
Maybe in the sense of unit types like a ground and air force there isn't much but I bet there are bountiful amounts of ideas.
You know how Wagners submerge underwater yet it's only to conceal themselves from above-water fire? Maybe in a successor there are underwater structures like in TA's Core Contingency:
http://totalannihilation.wikia.com/wiki ... sion_PlantImagine you expand upon that and there are better underwater structures, bases, defenses aside from torp launchers like a water-permissible laser?
I can think of many things...