A very interesting read.
I'm wondering why the collateral is needed. Proof-of-stake systems typically don't depend on the validator nodes having any stake. The community is the one that has to stake and thus gains governance power to vote for the nodes. If a node does anything malicious, the community will immediately unvote it. So what prevents nodes from colluding and stealing lots of funds and disappearing? In my understanding, the thing that prevents that is that every exchange runs its own node, so even if there is collusion, the colluders can't sell the stolen tokens anywhere. They won't gain anything, they'll just destroy their reputation and lose future rewards.
Is that your understanding also? Why do you see the nodes locking collateral as necessary?
This part isn't delegated proof of stake. It's more or less pure proof of stake to get assigned control of the multi-sig wallet. the ecosystem as a whole can be delegated proof of stake, but due to the external nature of the hive tokens there will always be certain limits and other things we can't program to overcome.