Bingo! I think the only thing is... the nodes verify all aspects of every transaction because a front-end allowing certain transactions is only a matter of convenience and not security.
The operators may be paid thru inflation or with Hive transfer fees. Collusion is a very real problem and it prevents a HIVE multi-sig wallet for instance from carrying a substantial amount. The system is Proof of Stake, and attacks can come from both holding transactions hostage and stealing outright. So a multi-sig wallet with a 13/25 weight could only hold as much as the lowest 13 signatories collectively have in collateral. The rest would likely go directly to layer 2 token purchase to keep the price of the layer 2 token high.
To keep transactions on the DEX working only properly collateralized trades may be placed, and only properly collateralized trades will be kept live. Additionally, only trades with-in 1% of the current best price may be purchased to prevent wash trading the moving average up or down and cutting out certain parties.