I hate multi-player, no guessing where my vote won't be. I also can't really see it going far from what it is at the moment in terms of player count ( not much chance of it increasing) and actual stuff you can do (scripts).
Really, the engine needs to be finished first. Not just added to and then onto the next thing. That is the reason GG is in the state it's in today. Not enough time spent on the right things or too much time spent on the wrong things; take your pick. There's soo many issues with GG, please lets get them fixed before we start asking for more new features!
I would hate to be in Lee's shoes with GG. Having a voting board decide the direction of coding, voted on mostly by non coders. I know even with simple projects (by comparison) getting the code done in the correct order helps massively. If you jump to a feature ahead of time you generally find yourself back at that code with each little update you make. It's far better to leave that code completely until your main engine is ready and has far less chance of major changes. It certainly saves time, which Lee is has limited amounts to spare.
By all means multi-player needs improvement, but when it comes down to the crunch, a multi-player standalone is very, very unlikely given it's need for Steam. Making a standalone multiplayer without steams api will not only take TGC a
long time it will still be a client server system and so pretty old hat by today's standards. TGC aren't likely to provide a server for this sort of thing; not practical at all. Really, multi-player is so out of GG's league I find it a distraction. This is coming from someone who has supported TGC from the start of the century

I have seen several multi-player attempts, none were good or easy to use. GG using Steam, is in fact the best they have managed to date (due to using Steam's api).
I would prefer attention to things that are more useful myself. Get single player working before worrying about anything else.
SPECS: Ryzen 1700 CPU. Nvidia 970GTX. 16 Gig Memory. Win 10.