I think it should work fine—you just have a single compound tx, txAB, with a list of multiple operations involving multiple coins, and when anyone reveals a Merkle proof of it as part of an exit, challenge, or response on one of those coins, they also have to reveal that it was included in the other path(s) for it to count. It’s a slightly different kind of dependency from what we’ve talked about in Debit but if anything this fits a more traditional concept of a transaction.