I've currently played a full mage, warrior and thief up to about level ~25 each, and to be honest I enjoyed them all, but now I want to start a new character. I want to do it on the hardest difficulty, and finish the game. Well, at least finish the main quest then do as much as possible before I get bored.

As I'll be playing on the hardest difficulty, I'll want a fairly solid character, and preferably one thats fun. My 2hander Orc warrior in heavy plate was pretty OP, especially with his berserker ability (3 shotting dragons) but somewhat boring too.

I'm thinking a sort of Battlemage might be best. A heavy plate wearing, 1hander + shield/spell that can sneak (up until 6x sneak attack) with spells focusing in conjuration. Some points would go into the basic restoration perks, and the rest into smithing/enchantment.

Something like this: [skyrimcalculator.com]

My questions are:

Is this build even feasible? Am I missing some major flaw.
How well do you sneak in heavy armour? Is there any point worrying about sneak?
How good is block? I never really used it as my warrior was a 2hander and my thief a dual wielder. I'm guessing I'll need it on the hardest difficulty though.
Is there anything you'd remove/add?
Should I put a bit of focus into alteration? All the mage armor is good, but that perk bonus is useless without wearing robes. Dragonhide seems sick though, although with practice I could probably cast it without the need for any perks in that path.
In regards to conjuration, should I focus on elementals or necromancy? Dead thrall seems like it huge potential if you find the right corpses, but then again atronachs are just easy.

Another build I've considered is a full destruction mage in heavy plate with massive HP. You can make a mage that has zero mana cost for spells in one path (in this case destruction) meaning I could invest all my gains into HP. This combo seems very, very OP, but perhaps cheating a little? Especially if you had dual conjured pets with you.

Cheers.