And before you respond to post it elsewhere, I have.
Just for a change of pace that would take advantage of the excellent graphics and rolling landscapes of many UT04 maps as well as the optimized net code, why not have a racing mod using the Manta or other vehicles?
It could have several modes.
Race mode - mantas race though numbered checkpoints that make up a lap. Checkpoint zero defaults to the start/finish line. Players start there, next to their manta's that aren't unlocked until the race begins. Every player has a link gun that only repairs and has infinant ammo. Manta's have a slow rate of fire, and each beam does little damage and no splash damage. Maps could have pit areas off to the side where, like in F-Zero, they will regain hitpoints. In the pit areas, mantas cannot fire and cannot take damage from fire. Vehicle performance would deteriorate near exponentially such that near the last few hitpoints, performance drops fast, but is hardly noticable for the bulk of the upper HP levels. Vehicles would not blow up, or if they did, would not disappear from the map and would still be repairable.
This way, you'd be racing while still having a small element of attack to slow the person down, the more damage you do, the longer the opponent will have to pit or manually hop out of the vehicle to repair.
Acceleration should be lowered so skill plays more of a role in hopping at just the right moment to minimize craft damage and deceleration.
The craft should be able to rotate faster (maybe 2x faster) thought it should not be able to corner faster. Think Star Control 2 where you can turn your ship around but getting it to go the opposite direction takes some time to get the thrust going.
Crouching or lowering the manta would make it accelerate faster, but have a lower top speed. This way, you can use it to corner better, but would try to avoid doing so if you could avoid it to keep speed up.
As checkpoints could be far apart and wide apart, skill would also be deciding the best route.
Forward would apply thrust, not holding forward would just have the manta coast, backward would apply reverse thrust (with lesser acceleration and top speed than forward thrust. Strafing would do nothing while racing. Turning would be done by rotating while holding down thrust. Shooting at people behind you could be done by letting off the thrust and turning around (as you'd still coast backwards). Of course, this could only be done in short burts unless on a straightaway. Turbo boosts would be available to help in sharp corners or to gain speed on straightaways, though they would take a while to recharge before another burst, like the jump feature, but with much more delay.
Another mode would be a "your it" variety, or for those who've played Carmageddon 2, "The fox and the hounds". One player would be it, and when it your clock time ticks up. When someone bumps who's it, they become it. The first person to have their clock reach a predetermined time wins. All those not "it" see where the "it" person is on the map, and a compass bearing to his direction. The it person loses the map and the compass bearing, as well as the ability to hop. So basically, one person runs like hell while everyone else chases him/her all try to ram him so that when they do they run like hell themselves. It's a very fun mode of play in C2. Each player and their time (or time remaining) would appear on the hud. Or perhaps just the top 3, the current "it" persons score, and the score of the person on their own hud, so as not to clutter the screen (though all could be seen on the scoreboard view)
GUI menu options could include how many laps to win, manta ROF, manta fire damage, manta max hitpoints, and "it" time to win, "it" game mode on or off, "it" mode all vehicle invulnerable to damage on or off, and "it" manta fire on or off.
If, back to racing mode, making a "pit area" is too problematic, then perhaps just have auto turrets default to the zero checkpoint that shoot at and heal whatever stays in range. The more damage you took the longer you'd have to pause to heal it back. A totalled manta would spit out the driver, and the driver would have to repair it before hopping back in. Perhaps even have it so that a totaled manta would be locked until fully healed, to make it that much more rewarding for an opponent to fully damage a manta.
The hoverboard is faster?! Cool! 