I wish SM did crossover group projects with all of their girl groups like the T-ara/Seeya/Davichi collabs! A group with Sunny, Hyoyeon, Luna, Amber, and Sundae from CSJH would be my ideal. With a less trot-ish song, of course.
Edit: Oops, I forgot about SM the Ballad, but I want something with the Sexy Ladies of SM!