I did this back when I first purchased Moho. It was derived from Illustrator files. The basic shapes were drawn in Illustrator imported and "cleaned up". She was originally going to be "simplistic" but I then drew the "highlight" shapes in Illustrator and used a soft edge fill in Moho... just to see how it would look.
As far as I can tell from using Moho since my purchase late summer (I am a fairly new user). I can't see any limitations over AI or most vector drawing tools. Considering AI can't animate anyway... there is no comparison... and I hate Flash for animating. I do use it to export AI to Moho.
I have successfully imported AI illustrations... yes... they require some clean up... but at least for me it hasn't been as much a chore as I thought it would be from reading posts here about it.
It certainly is a bazillion times faster than redrawing from scratch.
This is just a really simple test. I was goofing with bones and rigging and dynamics and switches... etc... The hair is a 24 bit PNG with an alpha.
I hope she isn't... too risque for the forum...

http://www.lowrestv.com/misc_movies/toonbabe6b.mov
http://www.lowrestv.com/misc_movies/toonbabe6d.mov
-vern