Yes but maybe I miss something. I'll answer point-by-point if you want.
    1. openness: LN over nothing can interop with normal LN, and LN over Liquid can do the same. No difference here.
    1. fragility: high fees are not that important over L2 such as Liquid, and flooding an L2 is unlikely. Not sure about griefing attacks.
    1. prepayments: I wonder if Cashu can fix this problem for normal LN
    1. hot wallet: wait what? why there's no signatures happening in Rumble? How would parties authenticate each other?
    1. custodianship: LN nodes are not custodians, who says they are?
    1. fun: no comment