You could just create players, until you can't anymore...
You'll find that 20 is the limit though. Just enough for two custom teams or a handful of players on 3-4 teams.
I was really hoping when I first got APF that we could do 11 created players for all eight of our created teams.
All part of 2K Sports efforts to avoid upsetting the NFL (and EA I suppose). What I want in APF 2K9 is to be able to create at least 10 custom teams, and modify the existing teams uniforms and names. That would make the Season mode much more interesting to me.
Actually, I'd like to be able to build a custom League and schedule too. If VC limits the number of teams to 24 or 28, you can't recreate the current NFL anyway, so that should keep the lawyers happy.