Tank hero that shields allies?

There is yet to be a champion whose threat is not damaging enemies --- but instead providing shields to allies.

So I was playing HotS the other day and I was playing [ACertainHero] -- whose W is to provide shield to everyone surrounding him. And I'm immediately reminded of the fact that, there's no tank whose threat is to protect allies. I mean maybe Braum, but he only decreases damage... ALL of the tanks' threat in League comes from CC and damage.

Maybe a tank whose function is: "you should kill him, or infinite shields" is useful. Instead of just much tankyness, wow hard to kill.

Here's my thoughts:

Q: Generic long-range poke. Can do limited damage, but reduce shield cd. Or increase mobility. W: Shield (as convention). Provides shields to all allies within range. Can have high mana cost to limit sustainability. Can provide additional shield if only one ally is nearby to provide support possibility. Can make shield explode to provide offense possibility. E: Mobility (as convention). Can jump to ally. Can jump to anywhere. Can jump to enemy. Anything to provide [some] mobility. Can deal damage/shield in the process R: I donno, more shields? You decide.

Basically I want an champ who is possible to be a support, who is a tank, who provides shields to allies if he is not killed, and thus is a threat that serves a an alternative taunt. Notice that included no numbers in the concept -- it is only a concept afterall.

And also-- If it is impossible, please tell me why, instead of just "omg your dumb no"... first of all, you're*... and second, provide a reason. tell me why it is dumb/impossible.

(I'm gonna get a bunch of "omg your dumb no" comments aren't I)