With the new outfit system any class can wear plate armor, or anything really. The forthcoming ceremonial outfit is a good example for that.
Is there any reason why we cannot transmute light armor skins onto plate armor, or etc? Lore wise I don’t think it really matters anymore. It would be great for the extra transmutation charge sales as well. It would also sort of fix the art team’s difficulties with creating decent medium armor sets. (I don’t suggest that they are bad artists, rather that sticking to leathery armor things with the gw2 gfx engine is anything, but effortless)