Mempool Incentive Compatibility

Agreed! Despite discussing both here (partially in the hope of producing some magic solution which addresses both!) they are best considered separately.

While stackable txs are vulnerable to this problem, that’s actually OK I think? Because if we have the introspection tech required to stack txs, I assume we can also use that to restrict total tx size. If there’s a healthy marketplace of people making stacked txs with reasonable fees with some frequency, you don’t need this of course.