Agreed that some escrow system is a good place to start, but the issue of the ~timing~ of the payload release is still the most important piece. A builder could construct a block, prove it satisfies some conditions, and then release it 4 seconds too late (to grieve the proposer). Thus there needs to be some party enforcing the timeliness of the builder payload. This is the inspiration for the optimistic relaying endgame, which we refer to as a “collateralized mempool oracle service” and the Payload-Timeliness Committee.
I don’t see a good way for this part to be automated, but would love to be wrong! I mostly wish we had VDFs lol