Here's a completely off-the-wall idea:
The players' union could threaten to ditch the NBA and start another league in the U.S. Players could nullify their NBA contracts. New teams could be created as corporate entities. Players could receive shares from a certain class of stock, with voting privileges and share of revenue, along with base salaries. The new league could be set up within 90 days. It would remain to be seen whether this new league could run more profitably than the NBA and provide as well for its players, but players could earn dividends from their shares in the league even after they've retired. Their shares could have seniority based on when they are issued. Obviously, new coaches and new managers could be brought in.
If the good players that people want to see (i.e., the players that create market demand) leave the NBA for a new league, the owners' investment in NBA franchises would go belly-up. The value of those franchises is really based on the NBA having the best talent. The ones with the real power in this negotiation should be the elite players (and their agents), and their leverage is the potential to start another league that they own. Other than the top players, there's nothing that the NBA has that can't be replicated.
These powerful agents shouldn't be threatening to de-certify the union and sue the owners for anti-trust, they should be threatening to "de-certify" the league.
If players aren't willing to take these steps, it shows that the players ultimately want outside billionaire owners to take care of them and assume the risk of running a profitable league. If that's the case, the players should make some concessions to the owners and let the owners earn some return for their risk.