Rewriting the Christmas Special is lower priority for me than rewriting the rest of the game. And, since it'd need to be tacked onto the end of the story (since Caroline, Sara, and Linda's stories would all need to be complete), the benefit of adding the content from the Special into the main story seems minimal.
Having said that, I can't think of any technical incompatibility.
I guess some of the individual scenes could be extracted and merged in, independently... But since the "reality" scenes are all Christmas/Winter themed, it's not obvious to me how to do so without establishing some common Winter period in the game, effectively tying them all back together.
I guess the fantasy scenes could be incorporated as dreams, without much difficulty. But, frankly, I don't find any of those scenes erotic, so I don't think adding them into the main story would be worth the effort.
As always, though, I welcome alternative perspectives!