This is a feature I’ve come across in a few other games usually known as the item transmog,
What this simply does is turn any regular item into a vanity that can be worn over top your physical gears.
It could also include the set sparkles from a set
For example, if you “transmogged” your demonic set into vanities and wore it over top your regular 115/farming set, you’d keep the demonic sparkles and effects as well as the stats from your physical gear!

This would allow for infinite ways to outfit your avatar, and especially for pvp and pve where practically every item set is just collecting dust in your inventory because you have to wear specific gear for those modes; having them become wearable over top your physical gear allows you to get more use out of them where you can really only show them off standing in a town.

This can be implemented in the form of an NPC much like the ones that enchant your gear, and will cost gold to do (this should help with the gold inflation as a nice bonus) -and cannot be reversed-

If there’s any worries about economy you can make it so any items that are transmogged become untradeable as to not flood the cs

I hope to see this implemented if possible, I’m one of the few players that loves to just sit and make many unique outfits so this would be a dream update for me
Thanks!