A Faceless Person changes height, weight, voice, body; from the Wiki:
The Faceless Men possess the ability to physically change their faces, shapeshifting so that they appear as an entirely new person.
Shouldn't the needed effect be more similar to Star Trek DS9 shapeshifters, rather than just pulling a mask off? The show seems to shift camera angles during these transitions, so it's not clear how the changes follow the unmasking.