I agree wholeheartedly.
Yes, there need to be limited jobs. The normal job rotations are way to boring, repetitive and rigid for me to enjoy playing them past the point of simply reaching max level.
Currently, BLU is the only battle content in the game that keeps me subbed. It offers variety, flexibility, customization in playstyle, and unique soloing opportunities. I am very much looking forward to BST to add some more limited job content. In fact, I would prefer that SE ONLY added and enhanced limited jobs from now on.
FFTactics Calculator job anyone? Mime?
Others have done a great job pointing out what makes current BLU unique and why it would not work in normal content without being dumbed down and destroyed...
I will focus on unique content you can do with BLU. My FC knows me as the BLU evangelist. Even some of its strongest opposers have come around to love the job when I explain its capabilties and even help acquire spells:
BLU spells are fun to obtain. Having them gained for free on level up would ruin the activity I have found most fun in this game. All spells can be obtained solo and it was a blast for me to do that. I also help others duo and trio spells. It's one of the few engaging solo and lowman activities this game offers.
The Masked Carnival is fun to progress through and offers unique challenges found nowhere else in the game. Completing its weekly challenges offers sizable poetics. Also allied seals, which can be used first to buy unique BLU accessories for glam, then to have an endless supply of aetheryte tickets, meaning free teleports for life.
I solo all my mog tomes on BLU. 4 any time I want in 11 minutes caustrum meridianum, 8-9 minutes Neverreap. Very fun to solo and I can do it any time without queuing.
I solo treasure dungeons on BLU. 3 golden beavers solo so far from the zonureskin map dungeon since the 80 cap!
BLU also makes old content faster, destroying fates needed for relics for example.
Try it out! It's a blast!!!