Don't know much about McCoy, but I would love it if Arians got the gig...
The biggest appeal of Arians to me is the HC experience he gained essentially on the job this year with the Colts after Pagano had to bow out. That experience of running the whole show is something none of the other candidates have.
His age, to me, is a two-edged sword. On one hand, yeah there's a chance he might not be quite as forward thinking, adaptable or energetic as some of the younger candidates. OTOH, this team is used to an older, fatherly presence and so the transition to someone like Arians may not be as jarring as a McCoy or a Carmichael who are only about 10-12 years older than our oldest players. Not that shaking things up with the veterans would necessarily be a bad thing.
Arians' credentials are rock solid in any event, especially when it comes to coaching up QBs and getting the most out of them in big games. Cutler could definitely benefit from that.