I think it’s incorrect to say mempool policy is flimsy. As of today, 99% of all op_return transactions are under the 80 byte default max relay limit. Policy is very effective at filtering out transactions on individual nodes’ mempools. In my opinion a consensus change is not necessary because filters in their current state disincentivise spammers to the point where they have to use exploits or bypass the p2p network. Because of this, its clear bitcoin in its current state is for monetary transactions only. If someone wants to put illegal data on chain by using an exploit or bypassing the p2p network, or in other words “jump the fence”, technically nothing is stopping them, but I don’t think the fault and legal responsibility lies with bitcoin in this instance. However, if nodes start to relay large continuous data chunks by default (ie, this behaviour is now supported by the network), I think some fault can and will be put on bitcoin. And yes the risk of miners having their block orphaned is important and is a reminder that the miners serve the nodes, not the other way around.