I don't personally prefer this approach myself, but I think they would totally be wasting McAdams if she's discarded after Strange 2. I believe Disney is being far too cute by possibly bringing variants of Fox AND MCU characters into this film anyways. Most audiences will think of Delta and Omicron when they hear the word "variants". It's a very lazy storytelling technique to merge the two ladies and really comic-booky, which I don't enjoy. But maybe they won't introduce Clea as a "variant". Maybe she's a "refugee" from the Dark Dimension who doesn't know her mystical heritage. And she's unknowingly been brought up as Christine Palmer. That would be a MASSIVE retcon, and sound REALLY comic-booky (again, which I HATE), but I wouldn't put it past Marvel Studios doing that. As I've said MANY times before, the MCU is becoming closer and closer to its comic book counterpart with each passing year. Instead of streamlining comic stories, they're actually making things more complicated. However, with the HUGE success of NWH, I'm still very impressed with the job Feige's doing.