Due to the nature of how costumes work (they have their own database entries and own item ids) and the fact that we have opted for using the existing costume section and removing stats instead of creating a third layer like official, I don’t think we will include a transmog system of that level.
However, moving forward I will be converting many equipments into costumes sets like the major weapons and back items and Armor sets, I have added a system to indentify the difference between an original equip item and a costume variant (the pink icon in the botttom left)
We want to explore much more interactive ways of obtaining costumes, for example Paris followers set will not be in cash shop it will be dropped in a Gacha from Paris loot table
Paris Wings costume will most likely be obtained by a quest where you must sacrifice a spare or older unused pair of Paris Wings to convert to a costume item (you would be given a choice of hero or rare)
This greatly increases the value of these costume pieces.
Due to these changes in costumes we plan to add a better method of storing them as well (probabaly a custom vault for only costumes)
A transmog System would make sense if we were designing from scratch or were not using the existing costume system in place, but in current circumstances I think these alternatives are just as good.
As we progress I will take in more suggestions for equipment to be made as costumes.