The double-delay problem is when Alice, say, doesn’t have the latest update tx fully signed (she sent her psig, waiting to hear back), and she needs to go on-chain. After U-1 blocks Bob then sends the final update tx, which in classical relative timelock ln-symmetry resets the timeout, resulting in a wait of U*2 before settlement can occur. Does your proposed change allow Alice to immediately settle or otherwise mitigate? Am I thinking on the wrong layer?
(I am genuinely very bad at reasoning about timelock semantics in bitcoin validation so bear with me)
edit: good thread linked on the CSV->CLTV transformation, think I missed that one