Addons should be able to increase that limit but instead save the data in local files.
On the other hand: Why do you need to save every tier set?
Tier sets are among the easiest to find transmogs. Just type Valor into the searchbox and go through every armorpiece and you got your Battlegear of Valor in no time.
But of course it's way easier to complain about too little space (in transmog and your storage space, I see a pattern here) than dealing with your compulsive hoarding disorder.