I found play a mage is incredibly boring, well in many game, not just skyrim.
What skyrim is doing bad is the ability to use multiple spell smoothly. look, you got to equip a spell... press favorite or use hot key and it still just do the equip thing.
Here, you already free 1 or both hands, why don't you're able to cast the spell directly with the hot key or from the favorite menu. Instead, got to equip the spell and launch the spell afterward?
I don't support enhancing destruction magic to where it is able to beat everything alone, but if there is more supporting effect within destruction spell, and you can cast different spells by pressing hot key only, i believe will make a big different.
Just a suggestion, make cross school magic in skyrim. Why don't make it so your ice bolt got slight chance to paralysis foe if you also learn a specific perk in another school. If doing so, Destruction mages will learn other school perks in order to improve their destruction effectiveness.
It seems to me that you want pretty much everything for nothing here.
Is it not perfectly reasonable that you should have to equip a spell before you can use it? Why should it be any different to anything else? I have an bow in my favourites list but I'm sure you would agree that it would unreasonable were I to be able to fire that bow just by selecting it in my favourites...
(At least I hope you would think it was unreasonable)
having to equip it first means you have to plan and think ahead about what you want rather than just sailing through the game just pressing the odd button - this latter approach does not sound much like fun to me.
Also - higher level magic school already allow a certain amount of implicit cross-school activity, for example destruction spells will make low-health enemies flee and cower, which is effectively fear.
Pardon me for being blunt but if you were to use it properly instead of wanting everything to be handed to you on a plate you might find it's not at all boring.
(Addendum: besides there's nothing say you have to play a pure mage, the game has more than enough freedom and flexibility in it to allow for all sorts of combinations of magic and weaponry. If you do play pure mage that's entirely your choice, so you can hardly turn round and complain that it's boring).