I feel like it's obvious Odium has another trick up his sleeve, besides the loophole Wit discovered.
So, one thought I had was inspired by the Sibling saying that their Light "makes the Radiants here virtually invincible."
Add to that my theory that the way Dalinar has set himself up to fail, as Odium says, is that there is no provision in the contract for what would happen in the case of a draw. I'm not sure how that would happen, but here's my unlikely, probably-not-going-to-happen theory.
The contract states that the champions must meet at the top of Urithiru. So, what if Urithiru has no top? Just send some Skybreakers in there with some supercharged Division and bam, the top of Urithiru is now impossible as a site for a contest.
Again, I don't think this is the direction things will go, but I would still like to bring it up to get some gears turning.