If you were making a Top 5 list of superstars to win the Rumble, no doubt Sheamus would be in it. With that being said, no way Sheamus wins the Rumble. That either goes to Y2J for bragging rights against Punk(and completely filling out his wrestling resume), or Orton to get hot shotted to the main event(and far away from the "you punch me, I punch you for 8-10 minutes fued" he had with Barrett. Boring!).
This is Mania time. Big name time. With Sheamus ability, he'll get to the limelight one day, but not this year. You saw what he did in the MITB PPV: he & Rhodes put on the best performance of the SD match even though Bryan won it. If they bring that match back to Mania, he'll be in it again this year.
I hate how the E pushes new upper card/main event talent, but how they've done Sheamus the past few months have been enjoyable for me. He shows personality in his brute force, & he seems to be the "show up, kick ass, leave" character that is always a favorite of mine(sure he'll tell you about wee ol' Ireland every once in awhile, but I dont listen to that). Now that he's been put on a pedestal, I enjoy to see inferior talent(Mahal, Slater, Barret, Miz) openly challenge him. It may make for an interesting story during the Rumble.
But to answer the question, what to do with Sheamus? I say have him, Barrett, Y2J, Cena, Ryder, & Cody(if he's not in a match already. If so, throw Kane in there) be the last 6 in the rumble with Sheamus eliminating Barrett, then Barrett helps Y2J from being thrown out and helping him eliminate Sheamus. Let that fued marinate in main attraction matches like Elimination Chamber & MITB at WM28, then they can have an Ireland vs. England Brawl at extreme rules.