is there a way for self custodial lightning to work if one of the parties is offline?

Zeus wallet uses my zaplocker protocol to get close to this in a lightning compatible way Matt Corallo also has a spec for this that is better than zaplocker, but it is not adopted yet See also my hedgehog protocol -- that's not lightning though

Good point. Maybe perfect was too strong a word. "Optimally"? Btw I enjoyed your hedge hog demo at BHB