This addon will add two features:

1. Tooltip Modification (1 additional line):

Examples:

Character is eligible to collect transmog and item visual appearance has NOT been collected.

2. Character is NOT eligible to collect the appearance, BUT there is the same appearance available for main armor type for this class (ex. Paladins can equip cloth, but cannot collect the appearance)

3. Character is eligible to collect transmog and item visual appearance has been collected from different item with the same model. Current item is not collected (and it will not add any model to the collection).

4. This model has been collected from this exact item either on this character or some other character.

There will be alternative appearances listed with "ALT" prefix for all cases except from #5 (completely not eligible to collect)

Note: It looks like it's currently the only way to know if the model has been collected while logged in on a character that cannot collect this armor/weapon. (Ex. Death Knight looking at epic leather armor tooltip which model has been collected on the same account Druid character)

5. Character is NOT eligible to collect transmog and item visual appearance has NOT been collected from this exact item on some other character