I think that model makes a lot of sense in the non-ZKP scenario, since you have to reveal some utxo but allow it to be a different one from the channel.
In the ZKP setting I think it is less efficient, as using the actual channel utxo as stake doesn’t reveal it.
Also, as you mention, this proposal doesn’t change the trust model as much; each channel is still backed by a single UTXO, you just don’t reveal which one.