I haven't gotten to play with spontaneity yet, however, I feel it's very limited in applications. Time spent using the JA could be time used casting the spell. Barring instant impact, I'd much rather see something along the lines of composure. A Job Ability that occasionally quickens spell casting but imposes penalties to melee. have the 2 abilities share a timer and also can make them be mutually exclusive. similar to yonin/inin, Seigan/Hasso and afflatus solace/afflatus misery. I feel it would have the same flavor and similar effect. This would also be a strategic enhancement to the class with balancing between the two modes of operation.