Enshrining some form of PBS is a top research item for MEV researchers to improve the trust guarantees of PBS itself while also opening the door to economic changes in the protocol enhancing consensus sustainability.  This ethresear.ch post from Mike Neuder gives a good overview of the latest research here and calls out some of the challenges with off-chain PBS and proposed solutions to ePBS.

A successful proposal would propose specification and analysis of an ePBS design that improves upon the state-of-the-art.  A key challenge of the leading ePBS proposal (with payload timeliness committees (PTC)) is the lack of builder safety upon a malicious attester reorg.  Single slot finality (SSF) would go a long to mitigating this attack vector and is called out here as an interesting research direction to explore when crafting a proposal.

Another open question for any ePBS is the extent to which it is “bypassable”.  Bypassability here refers to the fact that already we have large investment into low-latency mev-boost infrastructure and it is possible that any sufficiently decentralized ePBS design (required to actually enshrine) would not be able to beat the latency advantage of an off-chain, more centralized system.  Proposals here would analyze the current situation, either to quantify the latency advantage (perhaps working w/ the production relay set to get actionable data) or propose solutions (either infrastructural or economic in nature) to reduce the “cost of decentralization” incurred by any possible ePBS design.

Another promising ePBS direction is expanding the expressivity of the mev-boost auction following the PEPC research arc.  Refer to this post by Barnabe Monnot for further information.  A proposal exploring some of the aspects of PEPC would also be interesting.