If two teams come in, and they are granted three imports to ease their arrival, you need 14 players. 10th man at least for each could be any old random or ABL player, so make it 12.
It's likely that some players already in the league could jump ship and, if the points cap is managed well, spread the talent so new teams aren't struggling straight away.
And with two new, full salary caps available, it's possible that very capable players return from overseas to take the new money on offer. This season we've had Kickert, Barlow and Motum added. Guys like Jawai, Johnson, Ogilvy, Khazzouh, Newley, etc might not stay OS forever.
And then there are guys like Gruber, Dillon, Tait, Lewis, Trueman, etc that are not currently in the league. And college returnees like Greenwood, Hadziomerovic, Aldridge, Drmic, McMath, etc.
Key will be the starters or main rotation players. And having a talent drop-off from your starters to the bench is not bad for the league if each team is in the same situation.