BLM Post-Patch, and where to go from here.

[Galvuu]

Black Mage is not a burst job.

Increasing the potency of Xenoglossy further, with three stacks of it, is going to force us to use them in the party buff window, restricting our movement options, and generally not feeling fun to play.

While I agree with almost everything you're saying, this point isn't completely true. It kinda hurts me to say this, as I started playing BLM in HW where being a steady damage dealer was its thing, every expansion moved BLM away from that and more into a burst job.
This is the damage profile of the BLM dps on 12Sp2 in EW, a dummy fight, overlayed with the overall raid dps:


You can see that, for the most part, the peaks follow that of the general trend. By EW, a lot of mastering BLM was tied to actually fitting your burst (3/4 Xenos, Paradox, Thundercloud and Despair) into the burst windows by manipulating your fire lines to get the required length and mobility.
DT might go back on this trend, but I feel the triple Polyglot stack and Flare Star somehow further pigeonhole BLM into this direction.

As an aside, and this is an idea I picked up from playing Picto, making Flare Star into a slower cast (like 5s) with very high potency (think something like 700 or 800 before the AF multiplier) might help with mobility. I can't begin to describe how comfortable it is to be able to use Holy in White/Comet in Black and Swiftcast a motif to get 8s of mobility. I feel doing something similar with Flare Star, assuming they're committed to that horrid spell, is a good idea mid/long term.