There's a minimum viable level for professionalism though. If you can't pay people enough to be full time professionals and/or attract any players of the quality that are currently Super Rugby starters then what's the standard of the competition?
Clearly Shute Shield and Qld Premier Rugby aren't high enough quality to become a national competition that attracts a growing number of fans and can become the base for growing the game here. The quality has to be significantly higher than that.
Our revenue is almost entirely generated by the Wallabies. If you took all that revenue and invested it in a club competition and didn't keep bailing out the states, and let Ikitau, Tupou, Kellaway, Bell, Petaia, Marky Mark (Nawaqanitawase), Frost, Valetini (just examples) access higher salaries and better coaching than we can ever give them in France, we would have money to invest.
It might not be able to fund 18 teams, that seems fanciful. But you would actually have
more players on professional salaries than we currently have, at a higher standard (because the lower level Super players would enter this club game).
I don't think you can make the economics work for a club competition without letting the top earners earn top salaries overseas, however.