I'm pretty opposed to masking a weapon as a different weapon type, and I feel that weapons are going to be more telling, in the end, than armor is.
Way I figure it, given the isometric view, we aren't going to be able to see too much detail on the armor - Diablo 2 or 3 levels of detail, that sort of thing. which means that, by and large, we're going to be talking 20 to 30 armor models, tops, including clothing, robes, and all the edge lord stuff, for a good long while. But that's covering anywhere from 100, to several 1,000 variations - is that the heavy plate that is super defensive, or the heavy plate that provides bonuses to Warfare skills, or the heavy plate that is barely better than the heaviest middle plate, and supercharges Warfare skills? Or is it one of the esoteric heavy plates to actually enhance specific skills, like regen restoration and defensive and counter-counter abjuration magic?
At the end of the day, as long as the costume can only be applied to a specific armor type, or the result of applying the costume differs based on what it's applied to - Heavy Plate into Fright Lord Heavy Plate, for example - and you can tell the base armor because of it, you pretty much are going to know all you were going to know before.
Similarly, I imagine "Clothes" are going to be the armor set that gets the most skins applied - they aren't intended for combat, so you wear them in places you feel safe, which makes "turning" them into a tuxedo, or a little red dress, or lingerie, or swim trunks, or a Hawaiian shirt and shorts, or an Eskimo parka, or a yellow rain coat, "easy," game-wise. No one expects any of that to be suitable for combat, so, "clothes" is the "Show-off" option for any and all bling. And, let's face it, everyone, at some point, wants to show-off, even if it's just a little XD