WCW actually did have a brand extension, just not officially. WCWSN was it's own brand of show with Jimmy Hart booking the likes of Shark Boy and angles where Jim Duggan defended America (and a TV title he found in the garbage) against foreign villains like Steven Regal and Cuban Assassin.
Nitro and Thunder had a lot of crossover, especially at the end when the shows were taped on the same night, but in my memory the rosters seemed to stick to one show. I know if Sting ever showed up on Thunder it was a huge deal as his contract gave him that night off.
You sure do have a lot of need to discuss WCW, Turner Movie Classics 1982.