does anyone realise that she's actually lost her original face, since it is cut off in order to use the disguises? So if she returned to Westeros how would anyone know her unless she carries it with her.

One of the reasons Jaqen is in Westeros is to get information on dragons in Oldtown. The Alchemist that kills Pate in the prologue of AFFC has the same description as Jaqen's new face after he leaves Arya. Also, even though we see Pate die in the AFFC, he is somehow still hanging out in ADWD's when Samwell gets to Oldtown. The faceless men seem to be taught a lot of patience, and Dany has wronged so many people there is probably someone rich enough out there to pay the price for the gift. But my post you quoted was mostly lofty hopes and what not, not what I completely expect to come to furition, just what I hope happens.