Where we differ QH I think is just on emotional attachment to the clubs. Having not come from Bris or Syd I have none. It's a different story for a Sydney sider like yourself, and likely would be had I been one.
My view is that in the best interests of any 3T becoming a strong domestic competition the interests of the clubs must be disregarded. (E.g. your valid point about SU in the case of 3 teams).
I don't necessarily believe that is the right thing to do, or would be the best solution in an ideal world. Just think from the 3T's side, it would be best for them.
But to support your side of the argument, any damage to club rugby would limit the ability to be able to expand the base of the pyramid, in which case you could have the greatest competition in the world, but it would be no success anyway. For strong support junior participation is key I think. Whilst AFL and NRL's senior playing numbers aren't something out of this world different from Rugby (At least in the regions I know. Sydney may be completely dominated by NRL in that regard for all I know, and of course AFL does in Melbourne), where they stand apart is the amount of support they get from people who aren't and never have been senior players. This is because they grew up playing, and therefore watching.