Dropping South African teams would almost instantly increase the quality of the competition IMHO, so Trans Tasman works for me. And the brand wouldn't even need to change: Super Rugby is getting a bit dated, but could still work.
That isn't to suggest I don't love watching two Saffer teams knock six shades of shit out of each other, but really they don't offer much on tour and they'll win at all costs at home, even if it means 12 straight penalty attempts and 400 tackles.
The product with Aussie and NZ teams would still have enough variety in styles to promote all aspects of the sport, and allow us to take it to the next level. Go back to a Super 12 with, as I said above, 5 Aussie teams, 6 Kiwi teams, and a Pacific Islands team based out of Parramatta Stadium.
SkyNZ in particular aren't idiots, and they know that ITM Cup alone isn't going to keep their subscription rate up. They need a premier rugby product. The loss of dollars from South Africa is proportional of course, but the availability of a larger Australian pie is tasty as a long-term prospect.