A couple high level concerns/thoughts:
- I’m generally pretty loath to add things to the fork choice rule. We have no means of actually enforcing a particular fork choice rule. While PoS does give an incentive to find a schelling point with other validators, and defaults provide a very powerful schelling point, as soon as some other schelling point shows up you can very easily get trapped in the new schelling point.
- Currently we have a bit under 50% of validators who don’t extract MEV at all in their blocks. This proposal would essentially “force” all validators to do MEV extraction (or outsource it at least). I don’t think anyone believes that MEV extraction is a net good (it is usually rent seeking), and removing the ability for altruistic validators to voluntarily forgo some extra fees in exchange for being good citizens (or just lazy and following defaults) feels like a path that we may not want to go down yet. As MEV extraction continues to gain adoption, this argument weakens, but I’m not quite ready to accept it as a foregone conclusion yet.
Edit: I was reminded that you can still extract MEV even without searchers/builders, by traditional gas price auctions and speed. This mitigates the second point a bit, though I still am loath for formalize extraction into the protocol like this because it prevents exploration of alternative non-profitable-but-altruistic strategies like time based ordering and such.