Scratch

Well, yeah, let's just insert a 3d renderer and create some default lighting conditions... wait, people will want those changed, so we will need to add some bucks for that, which will make an uneven number of categories. That will look cruddy. Anyways, people will want a smoothed-off surface, so we will need some subdivision, which shoots up the poly/vertex count by a factor of 8. People will want transparency too, which basically throws back-face culling out the window. Don't forget the reflections! That also throws out back-face culling. The whole thing will have to be optimized to run at about 40 fps. Oh yeah, don't forget the paint editor! We will need to make a whole new editor that works with custom shapes (not just spheres and other primitives), is easy to use,  and runs fast too, because the youngsters will just be frustrated by lag.

Good luck.

[/rant]

Yeah, this whole 3d thing isn't going to work too well.