Only insanity could keep Caldwell around beyond the last game and I know you are not crazy. Here are the coaches you should consider:
Peter Carmichael Jr. (Saints)-Makes very good in game adjustments and knows how to get the most out of his players. Would create a good offense with Luck at the helm.
Joe Philbin (Packers)-He is orchestrating one of the best offenses to date, think he would also do well with a young QB.
Cam Cameron-see previous two, he has a pretty balanced offense, would also do well with a young QB.
I like Carmichael the best though, also hire Mike Singletary as the defensive coordinator as I think the 49ers are benefiting from the very tough squad he put together before being fired. I think he could attract some pretty good players.
I will give you my choices for GM in another post.