Honestly, if I was going to revise the armor system, it'd be a purely in-game thing. Classes would come with a base armor point rating, and could buy more later in the game much like how formalists have High Magic now. Once you've put your first ~100 build in to get to the equivalent of Formal Magic (ie 4 backstabs, or 4 profs and all the trimmings), you can start investing in skills to provide in-game armor points without needing to rep them. Flavor them however you like, with an in-game explanation that fighters are just that tough, so they've learned to better take a hit/rogues have learned to roll with it/mages have learned to more efficiently power Arcane Armor. Cross classes pick which they get.
Then remove AA as a ritual and point-based armor tags from the game. Armor tags are simply yes/no propositions, like weapon tags, that require an armor rep of some kind. It either is armor, or isn't. AA becomes a high magic ability that solely lets you have armor points without wearing or tagging a rep. Poof, no more have/have not problem for OOG resources, and costuming options improve because people can wear things that look like armor while not being practical protectives.
Heck, replace AA with an 'Armor Aura' ritual like Damage Aura for weapons that makes a rep worth more points than you can usually wear, and it'll still be popular without being the be-all end-all must have ritual.