I'm sure you could find teams that would be competitive.
As has been mentioned the creme of the NCAA are showcasing the next crop of NBA draftees. They would be too talented for an NBL1 team, and would probably give some NBL teams a run for their money. But then again, even if you got those teams, the NBA-bound guys aren't going to risk their health playing games in Aus, s you may only get their 2nd-tier guys.
Problem is that there's not enough interest in NBL1 to begin with, and really only the diehards would turn out to watch College ballers.
Another idea for the NBL1 might be to play "Inter-State" games, with the best talent from each state on show.
(The WAFL and the SANFL play an interstate game, and it generates a bit of interest.)
For International BBL, I still think the best idea would be to invite "NBA Branded" teams, featuring their G-League affiliated players. They'd be good competition for NBL teams, and with NBA branding would generate a bit of interest.