This code is kind of in its infancy. Also, yes, I know it's a stupid idea. I like stupid ideas.
Here's the branch:
https://github.com/hmaon/OpenXcom/tree/recruit_aliensRight now you just have to have an alien mind-controlled at the end of the mission and he's yours. Future plans include some kind of special brainwashing facility. Then perhaps a cloning facility. After that, chryssalids break out and try to overrun your base, I guess.
TODO: Perhaps don't let the player take off the alien's skin and replace it with XCom armor via the armor menu? Perhaps mutons can still wear armor, though? What's the point of having aliens on your side? Maybe there should be some new special mission requiring an alien infiltrator? I dunno, it's kinda dumb, like I said.
This branch is also the testing ground for on-demand loading of .SPK files. I'm using it to load inventory sprites for aliens. (Also works if they're just regularly mind controlled!) I got the sprites from another mod, the inventory screens here:
https://openxcommods.weebly.com/downloads4.html So, thanks for that!
A couple of screenshots are attached.