Interesting, but also....assumptions.
I'm quite sure the dev team has done extensive combat testing....with those new armors, making sure they are good but not over-the-top.
The only issue is that in case you want to min max, it's only viable to stick with 110 gear, which as you say, leaves little customization....which sux, i guess.

Also allagan scepter is in no shape or form, needed for BLM to perform in T1-5, since you need to kill Twin, to get it; and you can beat her just fine without it.
You dont need to mix and match gear to get acc cap. either myth or allagan works fine, as sets; and so will BC2 gear.

Anyway, i dont remember details, but they did say something along the line: you get stuff from levi, that you combine with something, to get something...
So maybe other 110 armors, than BC2...or just upgrade tome gear to 110, or swap stats on BC2, as you'll be able to do with maxed zodiac weps.
we'll see
But there's no *Fundamental problem* as you suggest.