I would like to suggest the possibility of job specific trusts that can only be summoned while the party lead is the job they are tied to and specifically boost that job.

maybe call them mentor trusts or something

Blu trust = blue mage that fights with you and boost blue spell learning rate
Pup Trust = lowers overload and increases puppet skill gain, maybe a puppet that acts as a healer?
War Trust = ranged dd that grants increased acc and maybe a regen effect?

not sure what would be needed to balance them but making a trust that balances a character until they can get the jp and gear to be fully functional at end game would be nice