The privacy side of the issue is valid for sure, but the trust model in terme'of custody is not so bad from what I understand, if there are enough Spark Operator involved at least. Any LSP could also try to cheat as they perfectly know that no is running a watch tower so... The most important issue I see is about privacy indeed, still but I can't unsee Spark as a good thing compared to full custody that many people used through WOS until now. I prefer to see the glass half full. But we can imagine informal Spark entities runned by federations "Liquid like", with blinded signatures on top of spark. That would be cashu on steroids actually. Best case scenario is obviously Ark + CTV + chaumian ecash.