Defining events seems much easier than defining identity.

But events X and Y are specifically regarding the activation of Clippy and Stapley, so a definition of identity would need to be included in order to prove the barrier to acausal trade that p' and s' are claimed to have. Unless the event you speak of is something like "the button labeled 'release AI' is pressed," but there is a greater-than-epsilon probability that the button will itself fail. Not sure if that provides any significant penalty to the utility function.