FOF is very compatible with TW.
same mechanics, just lots more stuff like the grid, power armour troops, drones and your other SF stuff.
You could easily put high-tech space invaders vs WW2 or modern troops, however, they'd be several tech levels lower and thus wouldn't stand much chance against a large unit of adverseries. You'd have to put a large army against say a recce unit to make the game any fun.