Here I have quite wierd concept, but surely I am not the first one to go for it. I think good name for it would behttp://skyrimcalculator.com/#204215.
Just as the name says, it's basicly Destro/Restoration/Heavy Armor/Block/Enchanting. Note that this build doesn't use melee weapons at all, it's rather shield in the left hand, and spell in the right one. Also, this build is kinda made for RPing purposes, but I will explain it in the text.
Destruction;
One of the priorities of this build is to get Flame/Frost/Shock Wall which would prove very useful in tanking, since opponents will be glued on you all the time. It would be the best to cast that before the combat, it lasts 60 seconds and it should give you enough time to best your opponents.
Augmentations - It all depends on the playstyle, be it fire, frost, or shock, it's of great importance to fill at least one of them in order to do some imporved damage to opponents.
Novice to Expert - This build is made for 45th level, that is somewhat average level where people get bored and create new character, so I didn't go for Master, because it's not needed. But it all depends on you, if you want to go further into this.
There are no dual casting thingies, because it's unrealistic to drop your shield in the middle of combat and reequip it right away when needed. That is why we will not go for dual casting + impact.
Restoration;
I don't think I have to explain this much, but note that Recovery is very important perk here, since you will be in heavy armor, you will need some magicka regeneration. Most of the armors have either Magicka, or some fortifications for certain casting schools, and there is lack of magicka regeneration, especially in earlier game when your Enchanting isn't high enough.
Enchanting;
We're not going for fancy double enchants here, Enchanting is just important for heavy armor since you will rarely find some who will suit your build. It's a good idea to fortify 2x Destro and 2x Restoration, or 3x Destro and 1x Restoration (23% is your basic enchanting fortification once you get Enchanter 5/5 with no alchemy). So you will have quite nice reduced magicka cost, but I assure you, you will run out of magicka quite fast anyway. That is why we need Enchanting here.
Block;
I think it's quite obvious and easy to comprehend it's perks here. I didn't go for 5/5 Shield Wall because I have quite a lot tanking experience, and I assure you it's a waste of perks to fill it up to max.
Blocking all together is what will keep you alive and do quite nice amount of damage with Deadly Bash. Also, Blocking is one of the reasons why do we use Respite (Stamina regeneration with health regeneration) so we can keep our stamina pool up.
Once perked, Blocking is also a great CC skills, with all staggering, disarming and eventually even knocking opponents down with your sprint. Use it wisely and it will surely keep you alive.
Heavy Armor;
Not much to tell here, but since we are going for 45th level, it's better to get Heavy Armor instead of Light Armor for armor cap, because we will not use Smithing. Conditioning is mostly one of the most important perks there, who will give you nice speed bost and more moblitiy.

Stones/Race;
Up to you, depends on your playstyle. But I wuld suggest Altmer for 50+ magicka, because it will be quite messy with Magicka/Health/Stamina points. As for stones I would suggest The Lady Stone (25% faster health and stamina regen) or The Lord Stone (+50 armor and 25% magic ressist). Also, The Lover Stone is good for start, to level up your skills faster.

Magicka, Health, Stamina;
I'd give priority to Magicka and Health over Stamina, since Stamina will mostly be used only for shield bashing and you will be able to regenerate stamina by Respite perk. If you chosed Altmer, I'd go for 3,4,1, but if you went for anything else, 4,4,1 or 4,3,1 will do. But after all it is your call.



I tried this build, I am 27th level atm with it, and I can tell I am having quite some fun. At the begining it's kinda wierd but once you get into it, it seems natural. And I can tell, it's much more fun than traditional Sword and Board style, because it's bit more challenging. I'd suggest you play it on any difficulty, I am on Expert now, but I'll switch to Master on 35+ when I get enough perks for this.
Hope you like it.

Oh and, Ward Absorb perk, important to use it when you're low on magicka and you got casters in front of you. It will grant you some magicka refreshment and as long as it doesn't break, you will be able to hold it up. It does great deal to get closer to casters.