No from the habs for a few reason:

1) the cap hit. OEL is a full roster player more and already has retention on his deal. Gallagher can still be retained on twice. theres more flexibility there

2) Gallagher while definitely being overpaid is far from a useless player. He has historically had elite possession stats and strong microstats. Even if he is never worth his deal he can contribute in a 12 man forward core. OEL will have a harder time doing that AND as a dman theres less wiggle room as its harder to bury a dman among 6 guys vs 12 forwards.

3) The most valuable thing for either of them to do cap wise is probably retire unfortunately and Gallagher is probably closer to that than OEL. Gally is more or less done this year and could potentially hang it up in a year or two. OEL isnt in the same boat.