BLM already has less buttons than most jobs, though I do agree from a QoL perspective that Ley Lines and Between the Lines really need to be a single button. B4 and F4 I would prefer to keep separate, but that is more personal preference.

The issue with rolling Blizzard into Blizzard III, or Fire into Fire III, is that B3/F3 have vastly longer cast times and higher MP costs (i.e. you don't want to be casting F3 in the middle of your F4 rotation), and honestly they are fine as is from a game play perspective (though I can see why the names may be misleading).

As for Fire II, it desperately needs as rework / upgrade; higher potency, shorter cast time, lower MP cost, all of the above, I don't care because as it is it's simply not worth using (in the general case) and leaves the BLM pre-level 68 AoE rotation feeling super clunky (assuming you don't just spam Freeze + Thundercloud which is basically as good if not better than trying to do a Fire II AoE rotation).