[Gandalf Parker]

Well a variable prize could be done by mod using the Scenario method. Id have to do a check but Im pretty sure that something shows up in the game.log that could be clued on to modify the mod file with a new version of the Champions Trident. Im not sure how the other awards would be done by mod file.

Edit:
come to think of it...
if the Announcement of the Arena were picked up then the MOD could be changed to downgrade or maybe even remove the Champions Trident so that major beneficial bonuses making it worth winning and having would not affect the next Arena combat. Then after the Arena was decided, the new awarded trident could be modified.

Edit Again:
Brain Fart. As little as I was interested in this subject maybe we could totally Gandalf the thing. Make the awards wildly random with wildly random effects. Every time the 3rd-party program sees an arena announced in the game log it could change the mod that the game is using in order to downgrade the previous award, then assign a completely surprising prize after the arena is won. Now THAT is something that would make me seriously consider sending a REAL competitor to the Arena. I LOVE surprise gifts.