I don't think they will add more slots just because of reaper and sage since they share armor with other classes and only take up 2 more weapon slots. Armor slots for multiple jobs is really only a pain when leveling because you don't want to throw anything out since you know it can be used for another job and it's nice to just have it when you reach the level instead of having to get it from the dungeon again. That is why after I do my first job to go through MSQ I tend to level stuff in sets such as doing all my casters at one time, that way I'm only saving one jobs worth of leveling armor and can get rid of it all once I hit 80 on them all and they go back to sharing the same gear. The only other reason you would run out of space is for glamour, personally I'm always at this point, but that is what the retainers, glamour dresser, and to a lesser extent the armoire are for.