I think the only realistic options are the pivots in Vegas, and I don't think anyone can make a convincing case any of them are a clear upgrade over Sheahan.
Last year at this time, there were people who thought Sheahan could be an elite third line pivot if he took the next step. I'm not sure if that is true, but he has a lot of tools.
I have little doubt he will do well in his own end and play responsible hockey. He has a sound defensive game. The only question is his production, but if he puts up 25 points, which is realistic, I'd be content with that.
Most third line pivots aren't going to dazzle you... I mean, the gold standard is probably Couturier right now, and he has never broken 40 points in his career. Most games I barely notice Couturier, and when I do, it's because I'm laughing at how offensively limited he is vs what Flyer fans had hoped for him coming out.
And to land Couturier a team would have to get their nose open... badly. That's just the premium nature of the position.