What you're doing here is very interesting from an Avisynth perspective too.
Drawing of vectors over video is very nice. Is it possible to load images/video as is now? I've tried, but so far unsuccesfully. It would be very useful for ex. coding an antialiased pan, zoom and rotate script(Ken Burns) for Avisynth.
Is is still beeing developed? CheesyFX - is that a joke?
Anyway if you want testers for functions outside the subtitle functions - you might want to bang the drum for this fine project over at the Avisynth'er hangout:
forum.doom9.org.