Block proposer/ builder seperation in SSV

A leading strategy for a transperent MEV market framework post merge is the seperation of block proposers and builders, as described by Vitalik.

Seperating the responsibilites of the current block proposing flow into separate actors can open a new market of block builders which will work to maximize their rewards by offering block contents minimize the fee the builders are willing to pay proposers.
Proposers on the other hand will want to maximize their rewards by chosing the highest paying block content.
The above can close the gap between small stakers and large pools who can enjoy economies of scale by operating secret mempools.

Open market and SSV

Vitalik proposed a market where:

1. Block builders make bundles and publish the headers of the bundles that they create. A bundle header contains a commitment to the contents, the payment to the proposer, and a signature from the builder.
2. The proposer chooses and signs a statement consisting of the list of bundle headers that they’ve seen.
3. Upon seeing that statement, the selected block builders publish their corresponding bodies.
4. The proposer chooses one of the bundle headers from the list they’ve pre-committed to, and publishes a proposal with it.

We can tweak this proposal to suite the SSV network. Instead of siginig every proposed block content, SSV operators will sign block headers which pay a higher (or equal) fee than the highest they've seen until that point.
When a block proposer contructs his block, he will choose the highest paying block content signed by a quorum of SSV operators. A proposed block will then go through a BFT round to reach consensus.

An SSV operator will commit to a proposed block if:
2. Block content has quorum.
3. Block content pays the highest fee the operator is aware of (which has a quorum).

If the BFT round fails to reach consensus, a change round is initiated with a different leader.

Selfish leader

One of the issues with SSV based validators is that a BFT instance has a leader which proposes a block. The proposer has absolute control over block contents which can lead to him including transactions which pay fee via a side channel to the leader directly.

A market base block content selection won't prevent a selfish leader attack but will minimize it by making the selfish leader compete with block builders for fees.