I'm guessing they will be keeping the A320s and A321s for busier routes. I would be very surprised not to see an A321 at LPL/MAN during the summer months. The loads they get on their AGP, ALC, PMI, FAO etc. sectors are outstanding and an A321 would certainly be welcomed by the North west public.
I don't see a problem with operating these aircraft aswell, a short course for both sets of pilots to get certification for all three aircraft and away they go! (Unless the engines are different which may mean maintenance problems - can they change the engine types?)