I searched and didn't find any other threads that asked this question. So if there is one already don't go nuts telling me. Just go read one of the many other threads extolling the virtues of Delta.
Which airline will be the first to allow regionals to operate the C Series and which regional will do it? I know this is purely speculation and I understand the concept of scope. However, scope is never set in stone. If you offer pilots enough incentive scope can change. I don't think 20 years ago people thought regionals would be operating the CRJ900 which is essentially a DC9-10. I don't think we'll see regionals operating the CS300 anytime soon, but the CS100 isn't out of the question. BBD shows it seating 100 in 2 class config. If you reduce the number of first class seats to 12 it could seat 105.
If you are only going to post this will never happen just move on.
Personally, my pick is Delta operated by Pinnacle or ASA.