I think there also is a limit on the number of players you can send. But the comment about needing bodies for training is the correct one.
Which is why with no reserve league we should have a Crew 2 and any player not making the 18 could play and even some of the 12-17 guys should be allowed to play as well and then they could practice with the team of GBs choice or both.
So... you essentially want to bring back the reserve games (not that they were a terrible idea, just that even with a Crew 2 not all those guys will be getting extra minutes on the team)