Do you love big bluegill?
I don't know if anyone produces them, but it would be interesting. I know there's a coppernose x green sunfish hybrid caught, probably a natural hybrid, in the old In-fisherman Trophy Panfish dvd and it's quite a cool looking fish.
I'm betting that there are indeed, HBG produced using a CNBG as brood stock. I doubt there would be any difference in both the reproductive qualities, or the maximum attainable size when compared against HBG produced by utilizing northern strain bluegills as brood stock.
if you were to produce commercially for profit would you select the northern strain because of its range?
Probably, simply due to the northern strain BG's versatility regarding water temps.