A bit embarrassing, but I moderate these forums and am not quite sure where to put this suggestion now that the suggestions are closed, but since ES2 is getting attention again I am hoping this is a good time to put this out there. I've been noticing people posting on the subreddit, steam forums, and some cases here on G2G their custom factions with OP builds, or asking for some to try out in multiplayer. A good, and somewhat easy to implement thing to add to the ES2 workshop would be the ability to upload these custom factions.

Also, some new categories on the workshop would be nice. Specifically, Galaxy, Planet, and Combat.

Last thing, hopefully this is my last chance to ask for documenation on to write AI mods, because the functionality is there but no one knows how to do it.

I second the ask about AI programming tool documentation!
I would add some sort of public xmls clean up request so assets are not linked 5 times in 5 different files and finally make the game load without warnings by default. =D