Advanced bot reports & UT3 technology
Tried playing UT3 Beta Demo... It's OK, but much worse than UT2004 in terms of performance. But what I liked there and what I would like to see in UT2004 is the bot support:
Bots should be able to report locations of enemy vehicles. Not Mantas or some Scorpions, they're easy, but Goliaths, Leviathans and Paladins (and also probably SPMAs), which are big, can cause trouble and move quite slowly. That way in Onslaught you can go to a node that isn't guarded by the Levi on maps such as ONS-RedPlanet.
Also, an option for players being able to automatically report things like that (and Incoming! for example) would be a good mod as well.
And on a side note, anyone tried porting WAR to UT2004? Those extra nodes could work well for some chokepoint maps.