Already other users pointed out that Potco is a MMO and MMOs have DRM because you must have an account. Even without subscriptions you would still an account to log in, I don't see any way to do that without some kind of DRM.
No DRM (DRM-free) is GOG's strongest point.
1. Even if tens of thousands of posible subscribers would convince GOG to get in this kind of bussines they would probably create a sister company to manage these things, so GOG wouldn't be in any way affiliated to DRM games (it would be a major setback and GOG community would be mad). But this is
higly unrealistic and I think you realize yourself this is not going to happen.
Also, the number of votes on the wishlist are not enough, or System Shock 1 would have been realeased already (it has 32.000 votes).
2. If Disney refuses to keep at least one server online then you could try what
Strijkbout said, buying the rights and assets of the game from Disney.
3.
The easiest way in my opinion is for someone to hold a private server. Anyway, a copy of the source code is needed for holding the private server, to acquire it legally you have to try Strijkbout's suggestion. A copy of the source code may or may not be found on the internet and it be against their EULA to hold a private server without Disney's consent.
4. If there are no private servers then you could mobilize Potco community to play other MMO, more or less with a pirate theme (Voyage Century, Florensia). If the community is the strong point then you could still have fun with the same people, even if you do a different thing. I think World of Warcraft is free until you hit level 20. I haven't played any MMO apart from WOW so I don't know if those games are any good.
And if you want to have some fun with some single player games you could try some classics like Planescape Torment, Heroes of Might and Magic 3 or Grim Fandango Remastered (when it comes out), right here on GOG.