The reason USDT migrated from Bitcoin was because there was a better home for it called Ethereum.
And similarly, there is a better home for ZSAs than Zcash that is also called Ethereum. You can see this in Railgun. Not only does it support permissioned assets but you have access to all the Defi lego blocks on ethereum too. So here’s a question. Why would someone prefer their shielded asset on Zcash, which only offers payment functionality, over Ethereum where you can trade it, lend it and plug into the massive ethereum DEFI ecosystem?
What will have to accompany ZSAs is increased functionality for them and that is probably the single biggest issue here and it goes to what Zcash’s identity is. This is also what i believe @ebfull mentioned on the latest Zero Knowledge podcast. Paraphrasing: there will be additional features needed that we haven’t considered but will find out about once deployed. Not to put words in Sean’s mouth, but that was the gist of it.
I can propose what I think one of those added features might be: faster finality for bridging of ZSAs i.e. Crosslink, which is a separate discussion, but also not really. I have so much to air about my concerns with Crosslink, but to give the simplest example of why it’s bound to be contentious: it has a safety mode. Unstoppable Private Money can’t have a mode where it stops because then it’s not Unstoppable.
I’m quite confident you could poll those in favour of ZSAs and you’d find a corresponding high support for Crosslink, while those not in favour of ZSAs would have a corresponding low support for Crosslink. This disagreement runs much deeper than just ZSAs.