The requirement that item match your primary armor type seems to be arbitrarily added for the sole purpose of increasing the time commitment required to completing your collection.
They did this so that it wouldn't feel mandatory to always go farm on a warrior which can equip everything. Also imagine raiding current content and there's going to be "that guy" that will always want every single piece of loot for his transmog collection. At least now he's restricted to stuff he can wear.
They could have also gone to the other extreme of letting all classes unlock everything - even stuff they can't wear. Do we want that?
The weapon equipment requirement still creates an advantage for certain classes.
True. Warriors can equip everything except wands. They will for sure be superior for farming weapon transmogs. Still, do we really want everyone to be able to collect everything?
The unlocking conditions creates a disconnect with how other collection tabs currently work. You loot a pet, it's added. You loot a toy, it's added. Heirloom, added. Oh this Leather piece loot you got won't be added because you aren't on a class that can wear Leather.
The armor thing might feel a bit weird I can agree, but otherwise I don't really see a disconnect. There's already a few class specific toys (see Fandral's Seed Pouch) and there will be even more class specific ones in Legion.
Certain quests are no longer available in game and offer different rewards, with how the current system is many items won't be added to my Wardrobe simply because my classic Loremaster was Class A and couldn't equip XYZ. To unlock questing armor/weapons sets, with the current system requires you complete questing on four different armor proficient characters.
This I can really get behind. I agree that quest rewards should be unlocked regardless of transmog rules, it's going to be really tedious to go and do Loremaster 4+ times (there's weapons too, not just armor...)
On Alpha this is highly inconsistent though. Some quests I get all the transmog looks (even stuff I can't wear) and some I don't. Have they actually stated how it will work?
Players who purchased items from the BMAH or Unclaimed Containers will be be ineligible to add extremely rare items simply because the item may be bound to characters who aren't the same armor proficiency or can equip the weapon.
Well, that's the gamble of BMAH. I don't think this is a good argument. You are not supposed to always get something useful from Unclaimed Containers.
Some items are changing armor types in Legion. A good example is the Scarlet Crusade set. Formerly a mail set, will become Plate Armor. Those who have these rare (now unobtainable items) will not only lose the ability to transmog these items, but won't be added to their wardrobe for other characters on their account.
Yeah, this is super weird. A solution I'd like to see is that we get to keep our old items as mail and then when new items drop they can be plate. That way it would at least not break any current transmogs.
Side note: you can actually get all Scarlet pieces except the pants still. They drop from Salvage Crates.
There are dozens of now unobtainable items that players may have held onto but can't be added due to the restrictions currently in place.
Sure, but they have never been transmogable on those characters, why should they be now?