I've heard some people say that BLU is getting "more mileage" by being Limited instead of a full job.

I'm not sure how they think that. Most of my FC didn't even touch BLU, I'm the only one that went for a 100% completion of it, and I got done before it's 1st reset, and the Masked Carnival isn't worth it's weekly rewards. My only reason to do this was because it was something I could do for completion, but I have no reason to touch it again until the Fall, when the next update to it is forecasted.

Furthermore, anyone wanting to jump into BLU late is going to be severely punished, as the PF isn't being friendly to their spell learning parties anymore.

If only 6.25% of players made it their main, that would more than make up for the "mileage lost" by not having more people pick it up as a side activity.

In it's current state, I do not want anything more of "Limited Job" content.

If at it's level cap, a Limited Job could perform at least as well as a Max leveled/geared normal job would at it's level
(eg. if a Lv.50 130 geared BLU was as good as Lv.70 400 geared jobs in unsynced 50 content)
I would at least consider running it for WTs

It's not like BLU is meant to be balanced, so let it be silly like that.

I see no actual reason to restrict it from Duty Finder. So what if it can be hillariously broken some times? Does it really matter in Level 50 content?

Change the "combo" actions by adding an additional "proc" effect. Meaning: yes, you can't petrify a Primal, but apply a "Petrified" proc to it that would at least allow you to use the Drill Cannons combo action, even if it's not petrified. (And for the love of... PLEASE remove that stupid low accuracy thing from it) Things like that.