Usually, people think about Merged Mining in the context of Proof of Work. But it seems to be possible to create a merge-mined chain that will be based on Proof of Stake. For example, it could start with zero initial coins and be pushed forward by providing a valid Bitcoin transaction. Then, people would earn that altcoin during moving their bitcoins. So, instead of getting Bitcoin headers and pushing that chain forward by providing 80-byte block headers, people could do that by pushing their signed transactions.
Also, there is no need to create additional commitments on-chain by making things like "OP_RETURN <commitment>", as described
on that mailing list. People could just tweak their public keys and reveal their commitments on the merge-mined chain. In this way, it is possible to make some Taproot address with some "OP_RETURN <commitment>" TapBranch, that will never be used on Bitcoin, but that could be used as a proof that such commitment is connected with this address (so also this amount, that is signed in the Bitcoin spending transaction, that means this altcoin can have consensus rules that will distribute coins based on such commitments).
