I have a few questions on the design
My understanding is that this design allows for multiple L2 blocks in a given L1 block, but doesn’t provide pre confirmations on those blocks, is this correct?
Are there more details on how proposing a block via the backdoorFee is done? My assumption is that the rollup’s fork choice is such that a trusted proposer block is used unless a backdoorFee greater than the floor is present in the L1 block for a given height. In the event there are multiple backdoorFees the highest paying one is chosen. I can think of a few potential issues.
First, a trusted proposer can be griefed at the cost of the backdoorFee, losing their revenue opportunity for their block while potentially still paying L1 fees. This can potentially be mitigated by paying the backdoorFee to the skipped proposer but this likely has other implications.
Second, payment of a backdoorFee to include a block essentially becomes a MEV auction above a certain price tier, this may be desirable when considering the L2s revenue collection, though at the cost of previously stated griefing concerns. This could also lead to a large number of non canonical L2 blocks being posted to L1.
Third, this all seems to be a layer on top of the existing L1 PBS. This leaves it vulnerable to what C-Node (https://twitter.com/colludingnode) calls Profitable Censorship MEV (link to talk).