Shelton Benjamin or Muhammad Hassan is my pick for SmackDown!. Benjamin has nothing left for him on RAW (besides what would be an awesome feud with Kurt Angle), and with him challenging for the IC Title at Vengeance, you could have him win and take the gold to SD!. Or you can have Matt Morgan decimate Benjamin as a last order from Carlito, allowing CCC the slightly easier win at Vengeance.
The WWE likes to surprise us, so why not have Benjamin "injured" on SD! by Morgan, then have Shelton send a replacement to challenge Carlito. He chooses Charlie Haas. Haas on PPV again would be worth it.
For some reason I can see Benjamin getting drafted to SD!, and not being able to face Carlito again, so they got the only two former IC Champions not competing in a match at Venegance, and put them into a contest on Heat. I think Val Venis and William Regal are the only two left. Anyway, have Venis go over cleanly, then have Venis announce he will win his third IC Title with his new manager by his side. Cue Trish Stratus (Hey, pairing these two up again at least helps Val Venis) and have the two passionately kiss on the stage.
Then you can either have Venis beat Carlito for the title, or have Stratus re-turn heel on Val, siding with Carlito. For some reason I can also see a Carlito/Kane pairing around the corner.
Muhammad Hassan is in the same boat as Shelton. There appears to be nothing there for him on RAW, so at least sending him to SD! (I'd have Khosrow accompany him saying he found a clause which allows managers to move with their clients) helps stengthen SD!'s mid-card, Cruiserweight and Tag Team divisions. It would also go with the WWE's policy of having Anti-American characters moved away from heel Kurt Angle. A face Kurt Angle vs. Muhammad Hassan feud would be top quality stuff, though.