I'm a big fan of the transmog system added back in Cataclysm. Not only it made me resub, but allowed me to player the characters I always wanted. But, the system have some big problems in my opinion that I would like to share:
1- Limited options for transmog weapons: This one is classic and everyone knows it, the most common complain is, you cannot transmog polearms into 2H swords / maces / axes.
2- Enchanting effects: This also a well known problem. Most of the times the enchant effect screws up the entire look of the transmog, it would be very nice to have a "transmog enchant" feature, so you can put your favourite effect (even none) into your weapon.
3- Long lost quest rewards: The transmog system only came out during Cataclysm. It means that all your only quest reward items you got prior to that, and deleted like any normal person would do, are lost FOREVER. The major problem I see here is that there are very cool and unique items that are quest rewards, items that you cannot find anywhere else! And since the system wasn't live back when you finished the uest, you can no longer transmog. It would be nice to have in any zone a particular NPC that sells all the quest rewards you already got, much like we have in Pandaria.
4- Removed items: This one is the worst problem imho. Every expansion, while it adds tons of good looking items, it also removes A LOT of old great items, such as Chains of the Scarlet Crusader, Necropile set, Fleshrender sword, etc. Before MoP it was said that you would be looking into it, but what we really saw in MoP was only a few troll items added in 5.2 and that was it. It would be nice to add those items back, in form of drops, quest rewards, Black market AH, professions, etc.
5- It's time to upgrade the system: I'm not saying the system is old, but it has potential to be much more! For instance, the feature to change the skin colors / textures of your gear, since we have TONS OF unused textures in wow's files.
6- You cannot transmog lvl 60 pvp gear, only if you have th title: People say that if the set were made avaiable, pvpers would feel sad because of the hard effort blablabla. But people tend to forget that, when TBC came out, the first honor lvl 70 set had the SAME models / textures of the old pvp sets. And you could get that in like a week of AV. And you know what? I don't recal ANY pvp saying "but I put so much effort into that, now everyone can have the same look I had!". Second, Blizzard made avaiable all the rank 14 weapons in SoO as heirlooms, and once again I can't see any old school pvper crying. Also, the he achievement is not account-wide, this means that if you got the title in vanilla, you may only transmog the set IF you play the same character you use to play like 6 YEARS AGO
So, this is it folks, this is the list of the major concerns of the transmog system right now. I would like to know if you have more problems to add to that list.
Thank you very much.
1- Restrictions, restrictions everywhere: Why so many restrictions to the system? Why can't a player wear common gear, when there are uncommon and even rare gear that look as silly / noobish? And why can't you transmog different kinds of gear, for example, plate into mail? There are also many gear pieces that share 2 and even 3 gear types. My suggestion, let your player be free to chose what they want to wear.
2- More space in the Void Storage: Players who devote themselves to transmog are facing a lack of space in their banks, void storages.
3- You cannot transmog Legendary gear: The stand point of "Well if everyone wore them, they wouldn't feel legendary anymore" went out the window with the legendary cloak. If you are willing to let everyone have a cloak, why not let everyone wear the legendary weapons they worked hard/farmed for?
4- Missing Parts: Certain sets are missing parts, like Hunter offset T8 parts.
5- some kind of x-mog journal added to the game. Not only would it help out to free peoples banks , but you could also allow all your toons to use items that you have picked up. Kinda like a BoA feature.