I assume you’re talking about cases where you might want to do cross-contract calls between rollups, rather than simply minting and locking operations, right? What would be required on the DA layers’ side to enable X-RU atomicity?
Can you still have have X-RU atomicity implemented on the L2s/settlement rollups (eg between to L3s) or shared sequencers? The idea of the zk settlement proposal is that if you achieve L1 base layer functionality escape velocity, you can do anything you want on the layers above.