One idea I would consider, if they look like they could get fans back in the buildings around May, is simply doing a tournament, with the "full playoffs" format only for say, the Semi-Finals to Finals at most. Set the seeds based on where the season ended. Lock in the top six seeds, and then let more teams into the tournament.
Not let every team in, but say down to the 12th seed in each conference, do that one game elimination tournament idea to get the 7 and 8 seeds, first round could be a best of three, then maybe a best of five Second Round, then back to seven games for the Conference and NBA Finals. Ending only a couple weeks beyond where they would normally.
The real scheduling problem that drags out the playoffs is during the first and second rounds anyway, temporarily cutting those down to best of 3 and best of 5 lets you do them in two weeks instead of a month. Even cutting just the first round down to a best of five potentially saves you a week.
The main reason I'd do an expanded "play-in" round is to get some games back for the lower/bubble teams but not really threaten the contenders too much. If they really can't get back by June, then I'd start thinking about not only a shortened first two rounds but also cutting out the conference seedings, seed by record only.
Main thing to preserve imo is the Conference Finals and Finals at seven games. Even if you have to just say Bucks and Raptors and Lakers and Clippers, sorry everybody else.
