Today I came up with an idea for pruning the utxo set that I think is simpler to implement than utreexo
I outline the idea here: https://gist.github.com/supertestnet/6aa3dbeb7cb749741c18ed9335a23a81
Discussion
What if all peers are pruned?
Pruned nodes already avoid signaling certain service bits (e.g. there is one that says a node is willing to share historical blocks, and they don't signal that bit) so just don't have them signal this service bit. Then your node can just ensure it has peers that *do* signal this service bit and it should be happy.