This is a very nice analysis. I want to point out two things that were said at the call.
There are three objects that are being broadcast during a slot, the block, the payload and the payload data (blobs). Today the deadline to see those three is the same one. When we scale to maximally utilize the slot each of these objects requires a different deadline. The data processing is only about broadcasting it, validation is free, thus, we want to set the deadline for its availability as late as the end of the slot. The payload does not have this luxury: it needs to be executed today and it needs to be ZK proven in the future. Thus, the optimal deadline for the payload is some time before the slot. On any system that has these different deadlines, the builder will have an option to withhold some private data. This includes, APS, Mev Boost, DE and slot auctions in ePBS (as opposed to block auctions) any system that has different deadlines for the payload than the data suffers from this option. So this is an inherent tradeoff to scaling.
Another observation is that there are two issues with this option: one is the value to the builder. Another one is the effect of missing blocks on L1. I’d argue that the value to the builder is actually higher than the naive approach that you only exercise it when the trade has gone against your bet. The issue is that the builder can run a secondary auction after the commitment and take bids for both winning and losing parties. This should make at the same time the option itself more valuable and also produce less missing blocks on L1.
An interesting point is that the transactions are fully visible during this option, it’s not like the builder is the only one with this information. Analyzing how the market can react with this knowledge, that is, that the post state is either A) The payload is executed or B) the payload is not executed as opposed to any arbitrary post-state, seems like an interesting problem in its own.
Perhaps the most important argument attenuating this problem is the above mentioned one on private order flows and searchers, given that these agents are the ones that would lose the most on missing payloads.
Finally one last comment is that builders that are willing to play this game will be detectable before they actually manage to withhold a payload. The reason being that the only way to prepare for such a withholding is by first introducing a private blob that has not been seen by anyone on the chain. Any large node on the chain should be able to immediately recognize this behavior. Not that it makes any difference in this analysis of course.