I'm thinking of an alien life form similar to a game called Creeper World. It was a strategy game where you had to place your towers in a way that blocked and pushed back an infinite amount of blob-like nanobots. The goal in that game was usually to destroy the source to stop the spreading of the blob. Something like this could work in this game too perhaps? It would at least be a unique 4x enemy!
Heh, funny you mentioned CW
Yeah, there is a slight CW feel to the game (but a slight one). With some races (parasites) there is a sort of "pressure" that builds up from their homeworld and you need to build "blasters" on your planets to stop/slow down the "creep"
Definitely such or similar mechanic is compatible with the game (on some abstract level of course). Also I slightly try to go in that direction when possible (I don't want to make it a traditional 4X with no combat most of the game and then one battle and everything is decided - a gameplay where you try to stop a wave of aliens is much more to my liking).
My biggest problem is what to do when the "creep" breaks through your first line of defence (it kind of dismantles slowly/quickly your empire then unless you quickly move your squadrons to make a new line). My first thought is to give the player cheap/free yet limited (number of guns) stationary planetary defences AND make some rule that aliens have to stop for a turn or two (like supply lines mechanic for example, or by some other means) after conquering a world before proceeding furter into player's territory.
Note: I have not tested nor fully implemented that part yet so I just speculate.
It would be cool if there were mechanics that rewarded using alien races as border states.
Yes... I think it would be cool too. Althrough I'm not sure I can make that one work.
The most fun I would see with aliens, is if we could sometime cohexist in the same planets, but following very different rules (for example no using the same ressources).
This could for example create situations where we easilly colonize alien systems (as they would not resist), but generate the dangerous situation of having to meshed foreign empires (what happends if they suddenly want to get rid of you ?)
I could also imagine :
dormant aliens (such as the parasite) in planets you own,
aliens who can travel through another spaceline network, and thus colonize planet you don't normally have acces to...
I am sure that there is plenty of room down that track o do interresting things there !
coexisting on same planet - No... Well, partially no. Each planet has to be owned by a single race, but after conquest the old race stays (so a single planet can have several races as inhabitants). Also there most likely will be hidden rebel bases and pirates bases (they would exist on planets owned by others).
dormant aliens - definitely yes, I was thinking of "war machines" that are burried deep below the ground and then wake up on turn 300 and start wreaking havock and attacking everyone
aliens who can travel through another spaceline network - Rather not... I was considering it but it would be quite messy (map wise) and quite confusing. Conveying to the player the information how it works would be not worth the effect I suppose.
(coincidentally, the engine allows implementing something like that, but I guess I would skip it
Note there might be an option for artifacts that collapse starlanes/etc (the engine allows it) but again, I'm not sure it would be worth the additional confusion.