Asuka vs. Io Shirai (she sorta counts as WWE now, right?). I really hope this match happens before it's too late. They're two of the most talented women in wrestling and it would be a huge shame if they never faced off.
I would have loved to see Joe and Lesnar at one point but not anymore. Even ignoring the fact that Joe is well past his prime, all of Brock's matches are the same. This wouldn't offer anything unique or special in the present day. You could pretty much swap out Joe for anyone else and get the same thing: Suplexes, Brock no sells, Brock kicks out of finishers, suplexes, F5.