Interesting proposal. I have a feeling there are more questions to be asked than answers. Will they be leveraging lite accounts (i.e. VSC or the upcoming HAF one) for the wallets?
decentralized custodial system
No idea how this could work, "decentralized" and "custodial" does not sound compatible with each other.
RE: Zypto × Hive Integration Proposal: Full Suite of Global Financial Tools