The problem is glamors fall apart if you glamor JSE stuff over non JSE stuff. For example, my WHM AF glamored over healer gear doesn't work when I change to SCH.
I'd also be supportive of changing the glamor system to allow job-specific glamors... but I like the OP's idea. Separate gear for tanks and healers. Having so many DPS sets also means there's less chance of healer and tank gear dropping.