This is EXACTLY what I've been thinking and wanting for a very long time. The way I see it: ......
There are all these nice outfits and nice hats available, separately, but why can I not use the hats *with* the outfits??! I can choose to not use the hat/helmet of an outfit, and I can choose to use an "armor" hat/helmet itself with oddly matching chest, leggings, etc., but I can't use my nice new Arcane Spellweaver's hat with my Adventurous Cat Outfit? Surely, the talented people working for ArenaNet can make this happen! And, my goodness, think of all the money there is to be made by doing so.... If I only use/buy outfits, and you come along with hats that are great and that I really like, but I won't buy because I can't use them with outfits, then by changing this (non)ability, you've just opened up a whole new market for yourselves.... not to mention how happy you've made your customers! Which certainly is a good thing when it comes to recommendations. You're happier, we're happier!
Pleeeeeease make this happen! 😉 😄