Out of curiosity, could you run Jumpdesktop w/keyboard and mouse support? That would allow your Mac Pro to do all the heavy lifting while you control it remotely. The only thing your iPad or MBP would have to do is receive and display the screen.
Theoretically, yes... except that I also work a lot of places without cellular connectivity (planes, subway, middle of nowhere in a car).
However: a bigger issue is workflow. When I'm working on my laptop I use MANY virtual desktops (generally 6-10!) and use all of the multitasking gestures of my trackpad to move through the system quickly. It would be a pretty large inconvenience to try to do that with Jumpdesktop and a mouse.
It's really just not worth it. Note: I didn't even buy a keyboard for my iPP... that's just not what I'm using it for. I bought it to be an awesome tablet (especially for taking notes) and it has surpassed my every expectation in that department. No reason to shoe horn it into doing something it really wasn't meant to do.