random thought:

if i gave you a signed bitcoin transaction that spends a UTXO, you can submit it and once it hits the network and everyone sees it, if it has RBF disabled, it's as good as cash, i've signed off on it, and it can't be reversed, but you can CPFP in case i gave a bogus fee rate for the mempool condition

a recipient doesn't have to trust it, just broadcast it and wait for the network to verify it

and it is basically cash, without an intermediary to trust, just a small risk of payment failure or needing to pay more fees