The current skin and transmutation system is annoying, restricting and not fun.
Also, collecting and using different skins is expensive and uses up too much bank and bag space.
If you want to change the appearance of your whole armour without losing your old skins you have to get 2 armour sets. One with the same stats as the old one, one with the new skins AND transmutations stones too.
Do not want!
Here’s an idea how it could work instead:
Transmutation Stones are a currency
Always with you, no storage space needed.
Skins are unlockable
Per character or account.
Once you obtain a skin it gets unlocked (holiday, living story, achievement skins, etc. too) and can be viewed in some kind of skin panel (think PvP locker but accessible from everywhere like the achievement skins)
The special skins that are an actual item with stats should go there too where you can withdraw them. They should be account bound (the trend is to get only one item per acc anyway and why should those be soulbound?). Ideally their skins get unlocked account wide too.
Templates:
Select locked and unlocked armour pieces, weapons, colours from your skin panel to create and save entire looks that can be then viewed (or even linked in chat for others to see) on any character.
Ideally there is a preview window which shows your choices immediately.
Transmutation:
There is a special panel with slots for armour pieces and weapons.
You select your equipment pieces you want to transmute and you select a saved skin template or create a new one with the skins (and colours) you want to transmute onto your items.
You then link your skin templates with your equip templates. This costs transmutation stones per item that gets transmuted.
You can link several transmutation templates to your chosen equip sets. (Existing linked templates can be modified (might or might not cost something))
You then can change the appearance of your whole equipment with just one click (this does not cost anything) wherever you are and how often you want without losing any of the skins.
Town clothing:
There should be an extra section for town clothing in the skin panel for their storage.
Ideally town clothing are skins too that can be put onto (or removed from) the standard town clothing your character comes with when created.
A toggle option to show town clothing instead of armour skins would be pretty nice too (there are far more immersion breaking things than that in the game)
With this system people would actually buy a lot more gem store skins and town clothing and maybe even more transmutation stones. At least I would.