The armor/weapon customization should be the same for that of the tabard. Example: Tabard has a base design(Blank white tabard). Through the guild monument, you can customize the different paints on your tabard. What if you could do the same for plate, like your suggesting with full black plate, but instead use a different model. This exact method can be used for walls, buildings etc, all customizable at the guild monument.
For example, lets customize the item, full plate helmet. You have the options between several different styles, that will then take over the base design for fullplate helmet (A resemblance of Milanese plate armor), and replace it with the one that you have at your monument. (excuse the links, they are safe) So for example: http://www.medievalcollectibles.com/images/product/large/ah-6110.png
, or maybe you'd prefer https://upload.wikimedia.org/wikipedia/commons/3/34/italian_-_sallet_-_walters_51580.jpg
. Im sure you get the idea, making it so that your padded, leather, chain plate and scale are just as unique to your guild as your tabard is. Not only will it help with larger troop identification in my opinion, but will also appeal to those who prefer the role play side of things. People can use ottoman style mail, Mongolian style Lamallar, etc, while keeping it balanced amongst the 5 sets, unless you'd prefer to go in depth and add strengths and weaknesses to the different armor styles