Currently they've come up with "glamour sets" that will store as "1 slot" (most of them) for however many items are in the set. (There are a few that, say, have two shirts but you can only put one into a set, etc.) It's my understanding this was to help reduce some of the "my glamour chest is full, need more slots please!" pressure.
Which isn't a bad idea, BUT, there are plenty of items that look exactly the same on the character, but are limited by job... and THOSE eat up plenty of space in your glamour chest, if say, you want to be able to use "this neat necklace" on glams for several of your jobs.
If when you put a (non main-hand/off-hand) item into your glamour chest it would make that item wearable AS A GLAM for ANY class... honestly, for many of us it would free up a LOT of slots.
And then if you remove the item back to your inventory, it goes back to being job-specific. Just make an over-code that negates the job requirements if it's in a glamour chest, then removes that over-code if you take it back out. Seems pretty simple.
The only exception to this would be our actual weapons/tools that shouldn't be glammed to look like something from another class... so you don't see a Warrior whacking someone with a WHM cane, for example, when IN a fight (or running around). So, exclude the main and off-hand items, but make all the rest "All classes" for when they're in a glamour chest and being used as a glam, please?
As to "this job shouldn't have a glam that looks like this other job," that ship sailed long ago, in my opinion. Others here pointed out the wild and often silly glam items, plus items that put armor on mages, or no armor on tanks, etc. For instance, I've seen burly tanks fighting in maid's dresses, bards in elephant gear, healers in Crystarium armor etc.
Note too that as they keep adding new jobs to play, that's yet more gear to worry about... and again, more that we may end up needing more slots for glamours because in the chest most of the items are job-specific. That's especially true for people who try to gain and master *all* the jobs.
Keep a notation on the item as to what job/class it's for and its level... but make everything (minus the weapons/tools) glam-wearable for all classes. We could clear out a LOT of "duplicate look" items from our glamour chests that way, and gain a lot of slots for the continuing "ooo look new shiny!" gear we keep getting as new stuff.