I'm not 100% sure that this would work but...
First you need to choose 1 Hume job to make Luso exclusive.
Make it so you need to have learned a Ability for the same job
Change Luso's recruitment Job to the chosen one and give him Starting equipment that will teach him an skill for his exclusive Job after the first fight.
Now go to change the recruitment for that Job into another one to prevent anyone in your team getting said job.
Finally you will want to look at different enemies formations and changing enemies from that selected job into another for everyone.
First you need to choose 1 Hume job to make Luso exclusive.
Make it so you need to have learned a Ability for the same job
Change Luso's recruitment Job to the chosen one and give him Starting equipment that will teach him an skill for his exclusive Job after the first fight.
Now go to change the recruitment for that Job into another one to prevent anyone in your team getting said job.
Finally you will want to look at different enemies formations and changing enemies from that selected job into another for everyone.