Due to how SVG requires paths to be done, I'd be doubtful that this could be done with Pencil, but it sounds like you've got the seed of a good idea for a new kind of tool, although I'd wonder if the calligraphy tool could be modified to have a "pencil-like" mode.
There is now a 'bucket fill' feature in latest Inkscape dev SVN, which works amazingly well for this.
Yeah, a pencil mode for the Calligraphy tool would be just as good. Although even the bucket fill will make my suggested technique a very practicle technique. I assume that's not coming in 0.45.1?
That's too bad - make sure bugs are entered on these issues in the bug tracker (they probably already are, but never hurts to have someone confirm and add info).
My issue using the pencil tool with a tablet isn't a bug. It's just very sensitive which makes drawing smooth shapes very difficult. I might get better results if I changed the tablet pen's nib. Photoshop is equally sensetive with its lasso tool.