That is why miners should be depending on full nodes for their relaying
needs, so it will be the nodes whose mempools matter.
That isn't how the system works, and it's not possible to make it work that way.
You can implement whatever rules you want; but miners don't care, they'll receive transactions around you. Even if every other node implemented some mempool policy; miners can just set up their own and people would send transactions directly to it.
Which leads to a question, why isn't Corallo's fast relay protocol in Bitcoin Core?
Because it has been under constant, rapid development. It's also only of limited interest to non-miners. I recommend adding it to contrib a while back, but the pace of development precluded it. Perhaps now that it's pretty mature he'll change his mind.