If the piece is Palat, then Subban needs to be retained down to Palat's cap hit of 5.3M. If it's Killorn, then a 2nd retention would be needed of, like, 50k. I think if we trade either of those guys before the offseason, we'd be seriously messing with the locker room and that's before we consider what asset has more value. Personally, I suspect both have quite a bit more value than Subban, but I don't know where Subban is at or where GMs and pro scouts put the respective players.
I think you're better off shopping him to someone that can fit him without it getting so convoluted.