Love the answers guys. Ok, why would any of you guys NOT want a full-blown or even half-blown (hybrid) Mac OS in your next iPad? #MacPad
Still not a good idea.
OS X is first and foremost and keyboard-centric OS. Pretty much every single function can be done with the keyboard, with little to no input from the mouse. Sure, if you get into photo or video editing you'll want a mouse, but from a purely OS standpoint, all you really need is the keyboard.
Getting a touch enabled OS X would mean rewriting a very very large portion of it. There's a reason why iOS and OS X are two separate entities, and I believe they should remain so. I hate how Apple has tried to merge iOS features into OS X (with most of them being not very useful on a computer). Launchpad is utterly useless. Pressing a cmd-space and typing 2-3 letters of the App's name will launch it faster than opening Launch Pad, waiting for the animation, finding it in the list and clicking it.
If Apple were to actually do so, it would have to be on some kind of tablet, not in a laptop of "conventional" form factor. Doing so in say, a rMBP is, as previously stated by many, unergonomic, and stupid.
The Microsoft Surface seems like a good try at this hybrid, probably the good way to go, but I still wouldn't want to use one.