Well, having known about this mod since about 1999 (I bought UT98 GOTY edition with your mod on it) as soon as I discovered it, I pretty much played with it on every game I've played. Seriously.
I was really pleased when you moved onto UT2k4, but I was slightly surpised, dissapointed and pleased with many of the things you did for CUT2, and finally got off my fat backside to actually post in your forums.

Pros:
C.U.T.T.E.R.: Weee! The ripper's back!
New ammos for old guns: the fire mines and Needles for the claw for example.
Proxies. I love those little buggers and their one-liners.
Ammo types. CUT was really cumbersome with all the different weapons (posion crossbow, explosive crossbow, yada yada yada)
Grenade launcher: Brill. I love lobbing a disruption grenade into the pack of bots following me when I've got the ball/flag. Ruins their day.
Cons:
I didn't really like it at first, but I'm getting used to, and quite liking, the changes to the crossbow from CUT. I miss the scope, but multi arrow fire is fun.
Cutter: Nothing Major, just the blades more *really* fast, or at least, seem to move alot faster than the ripper's did IIRC in UT98
Chaos Bike: It's a bugger to steer. (EDIT: apparently you've released a new version of CUT2 which as the bike 'fixed' so nevermind..)
The MUG. It's not so much the gun itself, more that whenever it's used my computer (which can handle a 23 bot onslaught/tdm game no problem) grinds to a halt when it's used. Not really your fault, I know. Just a pain.
Claw: Aww, I can't gouge lumps out of people with it anymore!

Proxies: I miss being able to just lob them, grenade style. Minor gripe.
Bastard Sword: Gotta admit, my favorite pastime in UT98 was getting this thing out and clobbering people with it. Third person makes it hell to hit a bot, especially if they've packing a flak cannon.

Sniper rifle/cutter gripe: When I'm playing onslaught, I often end up having to abandon my Goliath due to it taking too much damage from Cutter blades and the Chao Sniper rifle's standard bullets. Annoying, simply because IMO they should bounce off. But I think I'm right in assuming this is a game bug and there's nothing you can do about it.
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Anyway, enough of this, onto the idea:
Assuming you missed out the Relic of Redemption from UT98 for a reason, I've had an idea for another relic, which I've tried (and failed) to do myself.
Relic of replenishment.
What this relic does is it 'regenerates' your ammo, from a % of the total.
So replenishes ,say, 10% of the weapons total ammo amount every second or whatnot