Hi @mikeneuder, thank you for your answer!
You are interpreting my proposal correctly. Of course there are details that deserve more careful thoughts. For instance, if the builder fails to publish Txn B, but made public the ExecutionPayload somewhere off-chain, and the block was succesfully included, then the correct behaviour for the oracle would be to declare the block succesful and refund the block builder the deposit. Naturally, I’m still not sure about the precise optimal secure mechanism.
However, I disagree with you appreciation. Namely, that this wouldn’t be that different from using relays.
Without ePBS it is up to the proposers whether to engage in different block building markets. I see this mechanism as a good candidate to provide more reliable and sustainable markets. I imagine a scenario with more than one side chain doing this. They would probably compete for adoption, since from the point of view of the side chains it is an awesome use case. Blockchains are far more reliable than centralized systems (that’s the whole point…), and they typically don’t stop working. In case one of them do, we would still have the other competing systems, including possibly local block production.
If PBS is not a part of Ethereum consensus, then I don’t think Ethereum loses sovereignty due to an evolving free market of block building.
But my main point is simply that in order to decide whether to adopt ePBS, we should compare it with this scenario. Or even better, to provide fundamental reasons for ePBS.