It could make sense to have those that have dropped out and that will not be taken over as another persons 2nd character or NPC to be called away, after all an empire must have great need for people like Inquisitors. 

If we are sticking with the canon already written (Ha, LJ you have allowed us all to help you create a monster with its own canon now) the original cast were the currently graduated Inquisitors. We were the only ones left after the 12 years of training, the final Conclave. To integrate any new characters and stick with that canon we would have a few options.

1. Fudge the cannon and say the new people were graduates too. 

2. Say they were the year that graduated before our characters and have been seconded to this mission because the other have been called away. Though giving new-comers Inquisitor characters that would technically be senior to ours kinda irks me if I am being honest.

3 Say the new comers are final (11th) year Neophytes commissioned to aid the Inquisitors because the others were called away. Like Scout said they could be a sort of an apprenticeship status, promised that if they return they would then be ordained. That could be a good option to foster not only a mentor / mentee relationship but also could breed some interesting conflict.

I am in favor of option 3 than 1 in that order but that is just my two cents.

BTW LJ, I sent you the Omestri second draft.