Guild Wars 2

If I were to create say the Endless Quiver, and then buy the Prototype Fractal Capacitor with Power/Toughness/Vitality (and upgrade to ascended) and transmute them together for the appearance of the Quiver, but stats of the Capacitor would I be able to upgrade the transmuted item later to the infused version of the Capacitor, so that I still have the Quiver skin, but have the infused Capacitor stats?

Yes, Transmutation keep properties of an item and skin of an other, so you end up progressing your back piece, with different skin.