Actually, thinking about this overnight, I realized the DoS caused by carving out the “total fees” rule for block 1 entry is less than the one we already have.
You can already play the “free relay” game at the bottom of the mempool. In this case, there are three outcomes:
- Fees go up, you get evicted, you win a Free Relay.
- Fees go don’t go up, you don’t get to play this round.
- Fees go down for long enough, your tx gets mined, you lose.
The same game played on the 1-block boundary (with the Next Block Carvout) is worse:
- Fees go up, you get evicted, you win.
- Fees don’t go up, you get mined, you lose.
In addition, this game is more expensive than the tail-of-mempool game.
Unfortunately, you can play both games, so strictly speaking it does make the DoS opportunity greater. But it’s a fairly strong argument that this does not make it significantly worse, either.
This is a fair way out of my expertise, though: have I missed anything?