I really want DarKastle and Europe in the Air open during Christmas Town. They're both indoor, climate-controlled rides whose queues eat up potentially thousands of guests.
Yes, yes, I know DarKastle needs the winter season for maintenance. But what if DarKastle stayed open during Christmas Town, then underwent its full maintenance procedure, and the following season just opened a month or so late? With the exception of Spring Break (which is still nowhere near as crowded as Christmas Town and has dozens more attractions to absorb the crowds), it's not like the first month or so of the Spring season really gets major crowds anyway. I think having DarKastle open is vital to helping keep the paths in that area of the park somewhat navigable.
Plus, as others have said before, overlaying Europe in the Air with the Polar Express Experience from SWO's similar Wild Arctic simulator could prove hugely popular and relatively inexpensive for the park. It would make for a totally unique holiday attraction.