Depends on what you mean by “efficient”. My first implementation did build a merkle tree from the full utxo set dump, and that took about 10 minutes every time if I remember correctly (not optimized in any way).
With utreexo you don’t even need to hold the full utxo set to create proofs, so it is also compatible with light clients.
It is useful in this setting since we can reveal the keys (node IDs) used to create the aggregated key. Maybe you could do that with a ring signature also, I will look into it.
This is a great idea! I will look into that, thanks 