To be clear, a single block producer currently has control over a sprint, which is 16 consecutive blocks. The producer can delay and capture multiblock MEV for a max of 8 of them (any more and their backup will reorg them).
This proposal is for a single block producer to control a span, which is 100 sprints, which is 1600 blocks. (Please let me know if my info is out of date or wrong but I don’t recall this changing since the 64->16 sprint length change). Note that this proposal also mentions making span length “indefinite.”
Most multiblock MEV mitigation comes from the fact that if a block builder doesn’t propose a block with a transaction then another one will. This makes it unprofitable for a builder to “sit” on transactions that have value that is super linear with blocktime (most MEV transactions fall in this category).
The forced inclusion lists are a nice way to mitigate this problem, but theyre delayed. Competition is a better mechanism.
What’s unclear to me is this concept of “voting” that some of you are referencing but that doesn’t appear in the proposal. There is a validator-elected block producer, but that doesn’t necessarily mean that all validators vote on the producers.
It’s hard to make any judgement about the proposal without the economic architecture / mechanism design.
Also, let’s be straight forward - this is extremely centralized like L2s. That’s explicitly the point:
The difference is the validation mechanism (PoS consensus vs fraud proof), not the centralization of the sequencer.
But it also remains to be seen that validators will elect a sequencer that will behave as nicely as the validators currently are behaving. From FastLane’s point of view, this would be a fundamental change from a bundle propagation architecture to a full proposer-builder separation design - the latter of which is strictly worse for users if left unchecked.
Enshrined PBS would be ideal if additional safeguards for users are added to consensus (e.g., priority fee sequencing) - and perhaps this proposal is a roundabout way of implementing exactly that - but it’s impossible to analyze it without the economic / mechanism design.