Curious to hear what's the downside of this strawman idea to make the current blob market more efficient:

- 90% of blocks are built by the builder
- Rollups submit blobs directly to the builder's blob mempool or something like Flashbots RPC
- Builder’s mempool allows white-listed addresses from rollups. Adopt a less strict version of mempool rules:
  - Allow white-listed addresses to submit a vector of blob txs with varying blob counts (1-6)
  - These vectors can have different tip amounts
  - Implement a less restrictive tip replacement rule for these addresses
- Assuming a few rollups opt-in, the builder can mix and match blob txs from different rollups more efficiently than before, improving market clearing...