How is the Allagan equipment explained in canon?

[Endemerrin]

So, I had a thought earlier. We know that the Allagan Empire reached it's peak some 5000 years ago on what is now Eorzea, and lasted nearly a millennium. From the third Astral Era, to the fourth Umbral Era. Races such as the Miqo'te and Hyur didn't wind up migrating to Eorzea until the fifth and sixth astral eras respectively.

That brings up the question, however, of how there is Allagan equipment specifically tailored to fit Miqo'te (Holes clearly meant for tails, that tail-less races lack in their versions of the gear.) and even the hulking Roegadyn. In canon, I could imagine us opening a chest and finding Allagan gear tailored to fit a Hyur, for example. Even if there were an Elezen in the party who rolled on it, canon dictates the armor removed was once worn by some one with the build of a Hyur, thus it fits that character. But what about Miqo'te? Do we just carry around some scissors or metal shears to cut tail holes into our gear?

On top of that, how is it we're actually able to repair the armor? I imagine the metals, cloths, and leathers used to originally craft the equipment would have been lost along with the empire. I always pictured them being made out of some brilliantly engineered alloys and fibers dreamt up by the Allag, and so I found it hard to imagine how it all made sense from a canonical standpoint.

I mean, sure, as far as the game mechanics are concerned it's just a necessity, but SE has been very diligent about giving a reason for almost everything. I can't help but wonder what the reason is for all this, if it even exists. Was Allagan society mixed? Were there Miqo'te that traveled across the seas before the great migratory waves?