My thoughts on BLU atm include a few things that would probably be more a change to the "limited job" guidelines than specific to the job.
The first is syncing it to the same lvl cap as every other job in game rather than have it be behind and force players to keep an old set of caster gear just for that 1 job.
The second would be allowing it to queue as normal for duties that do not utilize roles to compose a party such as Eureka, Bozja, Deep Dungeons, etc...
The Third would be to make actual use of the BLU "weapon". It doesn't need to have raw stats added to it IMO. Instead I'd rather they do something like make a craft-able BLU weapon from every Trial and raid that provided weapons and instead of raw stats have said weapons provide bonuses to certain spell families, types, or elements.