With all due respect (and I seriously mean that, not being a wise a$$), but you've been dying on the 9th man hill for months. Of ALL of the things to really think about and stew over, that really shouldn't be it. That will work itself out. There are SO MANY factors that go into cracking that part of the rotation and most of it is defense related. Who can come off the bench and hold the fort down for 5 minutes a game. There is where the value is.
Now, injuries are something that can/will take any team out. We were bit by the bug significantly last year, starting with Ty in the summer. Then, Drej, Boswell, Z(nose) and Tomi last year. The year before we couldn't field a team for multiple games because of the flu running through the team and Tomi's mono. If Drej, Mirk, Tomi, Vaaks, etc go down, we have a problem on our hands that no 9th man is going to fix.
Another guy to focus on would be Coleman. We have him marked down as a major contributor despite not playing one second of college ball. Can he play defense at the college level? I have no clue, but what we all know is that Brad values that end of the floor to the point where you will not get off the bench if there's a crack. That's a legit concern.
There will be plenty of competition on the back end of the roster for a contributor to evolve. That's just how this works, especially given players transferring because they literally don't want that role. They don't want to take the time needed to develop. They want to play, thus the Lee departure. What you're looking for, those type of guys generally don't want for themselves and if they are ok with it, it's for one year and year 2 had better result in a significantly larger role.
The 9th man focus has been WAY too over thought. There are 10 things that would sidetrack this team before that concern would factor into the equation.