I would also like to hereby precommit to (assuming a repeat of the monetary award next year), donating the money to x-risk reduction next year if I win, and also chosing "cooperate" if a large number of people make a similar precommitment and "defect" otherwise.

I make the same precommitment.

Edit: Partially retracted. I'm committing to donating the prize to x-risk reduction if I win, but not to defecting next year if not many other people also make that precommitment. See here.

What do you consider a valid precommitment?