There is no perfect consensus on what changes could/should be implemented to the coliseum. I've taken everybody's perspective into consideration and I think I see the principles that need to be applied.
Regarding xp: "Trickle XP" is not an intended featured, and is basically a euphamism for botting. Thus XP in coliseum should be zero or severely penalized. I favor a 50% penalty over a complete nix (current setting).
Regarding coliseum loot: Splork and Josiah noted that this loot is out of place in coli since these items can't even be used in coliseum. Zlodiak and Josiah and others have suggested some of the loot is either OP or in over-abundance. I think the natural solution here is to move the coliseum loot to epic and raider mobs. Rather than take this stuff out of game, it makes sense to move it to the epic system. Kill raiders for boons and buffs and then use the boons and buffs on epic mobs. It makes a lot more sense than having a few highly scripted coliseum junkies supplying this stuff. As to the potion affects, I favor a reduction in supply to a nerfing of the affects. Also I favor raising the minimum number of groupmembers to use a heavenly scroll from 3 to 5 and make scroll not work in combat, force group to step back and do it. Same for lamb.
Regarding coliseum berries: Josiah and others have suggested that there might be drops in coliseum that could be used in coliseum (such as the old berries). I'm not inclined to do that, because I'm content with the scores where they are and don't care to upset the balance there.
So this would leave us with a coliseum where pretty much the only draw is going to be honor and drachma and glory and the days of people running it endlessly will dry up. I hate doing changes that piss off people I like and want to keep. But we have to base these decisions on some kind of principles, not what will anger particular players.