A Ghost Rider/Sherlock Crossover
Because I want to see Dr. John Watson be even more of a badass and take on what's left of Moriarty's lieutenants with the power of the rider. I might lean a bit on the first movie for that, though.
A Sherlock/Elementary Crossover
Because I'm extremely stoked about having so many different types of Sherlock Holmes in my life, one more cannot hurt. I want to see both Sherlocks deduce everything about each other and I want to see Joan and John being pleasant and all 'Yeah, he's my Sherlock. He's an idiot and I want to strangle him sometimes, but I love him.' Also, Mycroft(s).