Update the official SRB2 servers to 2.0.4 already. Hell, I think more people play the barebones 2.0 more than 2.0.2 and 2.0.3 by this point.
Add an optional method to prevent camping in Tag games for Hide & Seek esque tactics. Could be anything from revealing the position of the camper to forcibly tagging players who stand still too long. Make the IT marker change in colour when the seeker is out of rings. Add an option to allow players to keep their rings (and shield if possible, but not as important) when tagged, instead of losing everything when they get hit.
If a seeker fails to find all players in a Hide and Seek game, add a brief delay before ending the match and moving to the postgame score screen, wherein the seeker can F12 the remaining players and see where they were hiding. Make hiding players die in a single hit when tagged regardless of ring count and/or shields to prevent "furry shield" tactics, where an invincible tagged player could absorb all incoming shots and prevent a second player in the same spot from being tagged unless hit with an explosive weapon. Alternatively, remove post-tag invulnerability altogether.
(Done but in a different fashion. All players are forced to be solid in Hide and Seek, preventing this issue. I'd rather not kill hiding players, just leave them where they lie. -Jazz)
If it all possible, make race mode strictly client-based only. Allow all players to run off their own comps instead of being dragged down by sever lag. The players barely interact with each other as-is so I see no reason why racers should be burdened the same way as if they're supposed to.
Make the sprites (and the sprites ONLY) of the standard red-ring projectile specific to the character that throws them. This would allow for more customization of wadded characters, such as allowing the playable Eggman to retain his classic GFZ laser shot in multiplayer, without any cost to character balance whatsoever. Maybe even make custom shot sprites colour-coded (using standard colour-changeable green as a base) to allow the same sprite to cover different weapon ring types when customized?