I do, I think it'd be great, and very useful, to be able to summon a huge creature that is built like a tank and armed with a Dragonbone weapon!

Sounds cool, but you'd probably have to strike a bargain with the Ideal Masters. I don't think I need to explain why that's a [censored] idea.

So really I like the fact that we can't obtain it.

No, too complicated, and too dull magic is.

You can already conjure a http://www.uesp.net/wiki/Skyrim:Conjure_Boneman, a http://www.uesp.net/wiki/Skyrim:Conjure_Mistman and a http://www.uesp.net/wiki/Skyrim:Conjure_Wrathman so, why not?

That, or a Summon Lurker spell. I could use that one, too.