Well NYC gets 50,000 to 75,000 on Fox but I've seen it get 150,000 for bigger games. Those kind of numbers can beat the numbers that the digital F2A stations get at the moment.
As for a 2nd tier national comp, what I've suggested before is that at the end of the season all the grand finalists at 2nd tier level come together for a Challenge Cup style knockout to determine the best 2nd tier team in the country. That said, if you can turn NSW & QLD into genuine reserve grade with players from NRL filtering down, then it boosts the appeal. Also, there are a lot of local derbies in the 2nd tier comps that generate crowds and fierce contest throughout the season that can be structured for the TV schedule. It would be kind of similar to the College bowl system in American football where they focus on specific rivalry games.
I mean that's anywhere from 26 (1 a week) or 52 games (2 a week) for the regular season and potentially up to around 32 finals games that could be televised, though I suspect not all would.
It would require vision, determination and co-ordination to pull it off, but it would be worth it.