I do know of one man from Columbus, Ohio, who moved to Mississippi and joined the 17th Mississippi Infantry regiment, as he was my first person impression with my Confederate reenacting group, the 17th Mississippi (reenactment) unit.
As for wholesale regiments of Northern men joining the Confederacy, I simply do not know. However, if any forum can find out such information, it would be this one!
Wait and see and I am sure you will get an answer, one way or the other.
Sincerely,
Unionblue