heavy warriors have... heavy. Stealth an archers have light. Well mages will have clothes! the content is already made, and they can get perks that give them bonuses for only wearing clothes with their magic. Wearing fine clothes would be like daedric! only without the protection... cough*

Also, drop mana cost of duel casting to 2.5X instead of 2.8-3.1X; that's the real reason mages are being weak late game. 3.0X mana cost for only 2.1 damage? oh yay at least i can stagger him. Who needs stagger when you can just NOT duel cast an have enough mana to KILL them.

Well that could be a perk in the clothing section.

Also another perk would be getting 20-40-60-80-100% mana regen IN combat as the same as you get OUT of combat.

You might be interested in my mod... http://skyrimnexus.com/downloads/file.php?id=2275
It makes changes to dual casting, in combat magicka regen, and longer lasting alteration protection spells... and levels destruction spells to boot. I'm still working on improvement (browsing the forums to see what sort of things people are looking for which is how I stumbled across your post) so if you have any additional suggestions... let me know!