I'm so impressed and sold on the direction you are taking with your Sculptris application, I can't help but hope that you might, way down deep, have a soft spot for 2D animation and in possibly developing an application that parallels/rivals Sculptris in all of its best points - Simplicity, elegance, beauty and functionality which doesn't require an abundance of right click drop down menus and numerical entry property windows.
I even think there remains the possibility to incorporate "rendered" output from Sculptris as a basis for 2D characters, props and backgrounds that could be used in your new, revolutionary and controversial 2D animation application.
Why not 3D? Because I think the medium, with regard to imaginative cartoon animation, is incredibly limited and stilted. Just watch those early Disney and Warner Bros. masterpieces one more time, and you will taste again the wonder that was demonstrated, artistically, by the 2D medium.
Anyway, I'm starting to ramble and I just hope I can solicit a positive response from you regarding your secret passion to develop the best, most powerful and elegant 2D animation application yet designed. And, may it include the liberal use of vectors, bones and point animation.
I do like animation, and of course I side with John K in considering the classical toons to be superior when compared to most contemporary commercial stuff - the flat, spiky, garish Cartoon Network breed.
It's a tough proposition to (partially) automate this kind of work though, since a lot of the charm is down to manual artistry put into every frame of animation. A boned and keyframed puppet will never deform in as lifelike or endearing a fashion as Bugs Bunny rendered meticulously in pencil.
Assuming the user is a highly skilled traditional 2D animator, an ideal application would allow them to quickly and without mindless repetition sketch keyframes and produce fully inked and colored intermediates, possibly through some form of semi-automatic tracing, filling and morphing with good options for manual tweaking.
This sounds a whole lot like Flash/Toon Boom to me, but of course there should be room for improvement and simplification in the interface
3D skeletons and puppets could be useful for prototyping scenes and movement if you lack the hardcore experience and draftsmanship to "do it all in your head", but going directly from 3D into a traditional 2D cartoon output with outlined flat-colored figures is bound to look "fake" and cheap unless you spend more time and effort preparing it than it would have taken to just draw the final result directly.
I can't speak from actual experience of course, but that's what I suppose.
Can't see it happening within the next year or two, but I will probably do something with 3D and/or 2D animation at some point. Quick, painless and dynamic rigging/posing/animation of 3D characters is something I've wanted to experiment with for a long time, as is drawing an animated short (which might inspire me to make custom software).