Okay, I thought of another text task. I'm not sure if this is reasonable to be scoped with GSoC, but I thought I'd throw it out there so others could make the decision for me :)
One of the things that is annoying about text-on-a-path is that the characters get spaced pretty funky. I understand the spacing from an algorithms perspective, but from a visual perspective it just doesn't work. So, I (and I'm sure many others) end up manually kerning things so they look better. Inkscape should do the first pass at this automatically.
The Freetype folks have implemented in their library what they call the autohinter. Basically this was a work around for some Apple patents that disallowed them from implementing the full TrueType hinting. But, what it does is look at the shapes of the characters and tries to determine pretty good spacing for them, and it does a very workable job.
So, what I'd like is to steal the Freetype autohinter and put it in Inkscape. I don't think we'll be able to link to the code directly (which I'd prefer) because I think our internal models of things are different enough that converting them would be too painful. But, the algorithms should be roughly what we're looking for, and they've been tested and optimized over the years.
--Ted