Such solutions as encrypt mentions are already existing. And they cost hell of a lot, like Athena which starts at $ 5'000 a year (ending at 500'000. Yes, no zero too much. Half a million. US Dollars). While that's a little bit steep, it's understandable that it's expensive if you think about it. Because something like this means quiet a lot of trouble for the provider of such a service. And you have to make sure that everybody is happy even at peek times.
That said, sadly I think this will be the near future (as I somewhere stated more elaborately in another thread). You will have the use of super hardware at more cost than today buying and using it for some time. Not for the biggies, but for the small potatoes like us (if you look around, that's normal. The biggies get everything cheaper, we pay more).
I, for my part, don't like the idea of having my data and my apps in the cloud.
And yes, Cheetah is small enough to fit on an ipad. Though, for the new Ipad Pro this doesn't mean anything. They come with up to 1 terrabyte of memory. Yes, 1 terrabyte (still, the old 64 gb are available). They have enough power to render, too. The GPU comes with 4 GB of RAM, all in all a full fledged computer that hasn't to hide before anything else.
I don't like modeling with the pencil that much (with a small wacom), but the apple pen on an ipad pro is something else. You can really draw better than on paper, at least with less fuss. Well programmed, this could be a heck of a way to model away or to paint textures.
But it wouldn't be enough to just port cheetah for IOS. It would be necessary to create tools that are optimized for use with the pencil. and so on, quiet a lot of work. I doubt, Martin will have the time for that in the near future, while sooner or later the problem could solve itself with one OS for both worlds (where I sincerely hope it will be something that fits a desktop as well as the current OS).
Still, I'd like to get my hands on a real good, for IOS and pencil optimized modeler.