Neil from Second here! Great proposal, getting more diverse ways of verifying validity of VTXOs can only be a good thing. More elaborate responses on our forum, but two things worth correcting here: Bark (our Ark implementation) is fully open source and exit paths are verifiable from the output data alone, so the “proprietary environment” / “Implementation-Coupled Custody” framing is not a fair description of the situation. And mempool policy shouldn’t be a major challenge thanks to Bark’s adoption of package relay + CPFP in emergency exits.