My guess is that the burn from the proposed ASS replay order will be minimal for apps that take use it to prioritize cancels.

If an app sets the cancel priority fee to 1 lamport, then all the trades would occur at 0 lamport replay priority. This is the same as now. Txs pay an inclusion fee to validators and validators pick the order. There is no reason to set the fee any higher than 1 lamport. It’s basically a qos discriminator for each message type.