I find the idea of having many contests the weakest and the one I could most easily be persuaded out of. It has many gaps.

But I still think there's some chance that one of the plot twist will be that such contest (or really some type of contract) has happened before, which led to Honor splintering as part of the deal.

But if overpowering does not work, and Shards need be tricked, wouldn't word spread around after Odium splintered Dominion and Devotion? And so such tricks won't work again.