Problem is the talent pool is thin enough as is. Up the international imports from 2 to 4 and cut some of the grade cricket/retirees out. Expand the salary cap and consider some private investment (not private ownership but perharps a minority holding). The BBL is currently losing the best players to the Bangladesh Premier League of all competitions!
The tournament has added six rounds to the format over the past two years and crowds have dropped by an average of 9,000 spectators as a result. Condense it back to six weeks, same length as the IPL and time it exactly for the school holidays.
Seven will do better next time, but an entertainment product like the big bash is reliant on a solid TV output and neither broadcaster is giving as good as 10 did.