There are pros and cons either side but I think a good approach might be to cover bases with two comps, one more or less in each season. (I've written a lot of this before so it might be a repeat for some people.)
That factor about monthly salaries of imports could be crucial. Let's assume that some elite players (including imports) work to a monthly salary and others could be hired for a year or something like the current season.
Firstly, keep something like the current NBL where it is now, but slightly reduced salary cap, extra teams and third import allowance. Import allowance will make it easier for all teams to stay competitive and under the cap. Slightly reduced salary cap or leave it as is but make it possible for regional teams to stay competitive without overspending if they don't want to. Slightly condensed schedule.
Assume 10 teams or more if there's interest. Have each team play the other 3 times, once home, once away, and once in a regional area perhaps (Tas, Canberra, Darwin, Fremantle, Mt Gambier, etc). That will give 27 games to the current 28, so similar enough for players. A TV deal won't be crucial for this league which will fall back to NBL.TV only if it has to. For this reason, regional teams/games and small crowds at regional locations won't be the end of the world.
Then add a condensed second league in the optimum period to give access to the best talent and, where possible, avoid AFL. Find out from TV suitors (if they exist) what they want - shorter games, longer games, earlier, later, condensed season, etc. Pick the strongest, big-market teams (Perth, Adelaide, NZ, Brisbane, Melbourne, Sydney gives a reasonable league to start with) and with a shorter competition and fewer games, let them chase whatever players they can. These teams might try to get top flight imports for two months, or Joe Ingles or whoever.
Allow clubs with teams in two comps to hire players to play in both (for about the same amount of money, if they can). Allow players to suit for Townsville in one comp and then jump ship to Perth for the other. The idea being that a bench player for the existing NBL probably wouldn't make the cut for the premium league.
Easier access for new teams, more opportunities for players, more basketball across the year, good way to test what works and what doesn't, can make a TV-friendly comp without completely nuking regional teams and the jobs they bring, etc.