I'd be willing to expand to 32 teams, split into 4 divisions of 8. Play every team 2x for 62 games. In division plays 1 extra time for 7 more games. Then a few "floating" match ups based on previous seaosn standings to get extra games where the best teams plays. Say division leaders all play each other 1 extra time. That gets you to 72.
But ultimately I personally wouldn't go any lower than that, even that level feels like a big loss to me. I like watching regular season NBA, even in the doldrums. Cool stuff happens, bit players step up. Part of the appeal of the NBA to me is you don't need to wait a week for the next game. Also: I worry how it would effect ticket prices. C's tickets are already outrageous, if there was 20% less games I worry it prices a lot of people out.
I'd probably even prefer to keep it at 82.