I think it would be cool if certain lore backgrounds would influence the units strongly. For example, let's say that a certain tech got mass-produced over and over again, being modified only slightly depending on the conditions, explaining how all the chases are so similar. Or let's say that a faction belonged to a wealthy planet/company, with its members seeking to make the most of their limited space, while dealing with pesky units stealing the banks. Or maybe a planet suffered massive devastation, so units were designed to cheaply and quickly reclaim it.
I especially like how StarCraft tackles this topic, even if their factions (outside of unbalanced coop) are limited. (just 3 races) I also like how "Starlight" was originally a terraform weapon.
I think that this idea, if polished, could make for a very cool RTS. I don't think it would be as feasible for Zero-K, as the engine is old and unwieldy, so it would definitely be cool to see in newer projects. (But, if a modder makes something cool with it in Zero-K, my respects to you.
Shaman, you could implement it into Future Wars; I'd like to be your ideas man.)