Not a problem,
Unfortunately tackling the foundations of a rock solid implementation is the core motivation for me. I'd like to have the basis for a very general SMIL implementation, that could possibly handle any animatable attributes.
Doing a solid implementation is attractive, it'll take longer though. Just make sure that you have these abilities:
1) To take the current and next keyframes and move between them, displaying the tweened result at any given time. 2) To create a new key frame from a tweened (i.e. not really there) frame by editing it (make sure to display in your timeline where all the keyframes are) 3) You'll also need to be able to play animations in inkscape which would be interesting to see since I've yet to come across one that was fast enough. 4) Make the UI simple, only use ideas from existing animators if it makes sense to do so. You want to remove most of the complexity from the user and allow them to edit that complexity at their will.
I know from editing animated svg files that it's a very interesting task, even in a text editor; the most interesting animation abilities to me are animating paths since they're the hardest to visualise and the most interesting to tween.
Best Regards, Martin Owens