token miners who will work to the a new token signal readiness to secure that token by posting a public key to the bitcoin blockchain along with a collateral and possibly a block mined from a side chain, or some other signal proving sufficient participation (allows for non-blockchain tokens).

coin moved to the new token set is sent to a multisig wallet consisting of miners who have signaled readiness, with nlocktime set to some time in the future

coin sits in that wallet - the new token doesn't even have to be a chain, it could be a DAG, or some other mechanism - following whatever rules it pleases

any time, miner of the new system can move coin back to the main chain... trivially and following whatever rules are need. also, any time a miner fails to follow the rules of the new system, they lose their collateral

any sufficient consortium of miners/participants in the side chain can, of course, steal that coin...but that is true for all sidechains - and to some extent bitcoin - anyway

does this seem too simplistic or weak in some way?