We could trade Marleau to Ottawa for MacArthur. His contract is insured, which means they would only have to pay like 20% of his salary (aka ~900k of it), but if Marleau goes there and retires, they get more cap to help them reach the floor and wouldn't have to pay anything. That's a pretty big assumption, but maybe Marleau is willing to do it. Toss in a decent prospect (maybe someone like Rasanen with some upside but is kind of buried) and you may be able to get something done. Considering you help Ottawa on three fronts (more futures, less real money, more cap money), they may strongly consider it.
Marleau would have to want to retire though. If he's going to play, it's going to be here.