The problem with Sheamus is that he's not a good face. When he had his face-turn, it came across as forced and unnatural. He was either trying too hard, or pushed by management to try too hard. Either way, the fans notice these things. The problem now is when he eventually returns, he will receive a pop and have the interest of the fans for a few weeks, until his comodity fades again.
I think the best thing to do (aside from having him turn heel again) is to play an anti-hero. Stop pandering to the fans, and start just wrecking people. Everyone from heels to faces. That will come across as far more natural, and I think the fans will appreciate it more. The role of anti-hero was designed for someone like Sheamus. .