The easier way to explain it:
I want to buy an armor, but... also want to see how it will fit me. Which skin i'm actually buying?
Like Guild Wars 1 dyes. This is an excellent tool we could easily have. Like WoW "ctrl+click" (don't kill me for quoting evil words xD).
Being able to transmute skins encourages us to seek more styles either armor, weapons, etc.
What do you say?