Ois: Those close enough to each other along the globe should have less an issue.
But the quick suggestion would be (1) to [GOG-Players] title the game session and see who joins. Or (2) Voice it here, say 'I will be running a game in 'n' Time Units' or something useful.
Get some people into the game first for those new and those who need to learn it a bit before organising something major. The U1/UT99-Gold online is one of the more friendly and welcoming multi-player communities I've come across.
It would be great to see an organised scheduled tournament with the GOG player base though.
Whatever conclusion you come to, plase take into account the existing naming scheme, i.e. servers named and owned by existing clans and the individual players, too.
But I can't agree more, the multiplayer community is very friendly indeed and you usually feel welcome whereveryou go to play. Actually, Unreal series is the reason I'm hanging around here. I have actual physicl copies of both the original Unreal and the GOTY edition of the first Tournament. I only have time to play occasionally.. I think it has been half a year since my previous session.