The thing is, both Raistlin and Elminster are permitted to draw on special kinds of magic because of their 'unique' status.
A fair contest to all participants would require the arena to be held on a separate plane/different planet where NO EXTERNAL FORCES would be able to interfere.
This would nullify the cheese of Spellfire, Weave, and Raistlins Godhood (and possibly the PCs if you want to argue that far into the future).
ALL participants would then be on an even keel, able to fight with magic as they see fit - with the most powerful actually prevailing.
See how a fair contest works
