I think the idea has some merit, but as evidenced by comments in this thread, it would be a hard sell.
You would need to be clear that this isn't an alternative form of international/Test RL, but a tournament of provincial regions with perhaps a different/looser/residency/birth/Origin/whatever type player qualification criteria, or almost a super "club" competition.
While NSW & QLD are obvious entrants, in the cases of the England, Wales, NZ, France etc I would look for alternatives in name/jersey (keep traditional colours though) to their Test sides.
For example, NZ would enter the tournament, but not be branded as the NZ Kiwis. As pointed out earlier, the NZ team in the 1997 Tri-Series were not the Kiwis, but they still drew a sizeable crowd to support them in Auckland.
I haven't thought about it too deeply (and maybe that shows!) but a regional tournament isn't a bad concept, and might just work - few thought in 1980 that S of O would attract the interest it did.