Did anyone come up with a solution for the case where some tx might be included in a block but the block is withheld? I’m not sure I entirely like the idea that the owner will attempt to exit and be challenged by the operator, thereby revealing the information required to properly exit.
The other option is to allow the owner to sign off on a message that allows the new owner to exit from the coin. New owner provides signed message + exit proof for last known tx (owned by old owner) + hash of tx from owner to new owner (may or may not be included in a block). Tx from owner to new owner can’t be used to challenge exit unless actual new owner != exiting new owner.
The signed message from the old owner to the new owner would basically “bypass” the child chain and complete the payment on the root chain. Standard challenge rules would apply except with the tx that may or may not be included in the child chain as the tx that’s being exited.