Okay,
So I think what this comes down to in general, is that I'm not in favor of extensions publishing APIs. I have no problem with one extension calling another on what ever is selected (ie one effect using another), but I'm really against publishing an API and having another extension use that API.
At my heart, I love theoretical computer science as much as the next guy (okay, probably more than the next guy), but I don't want to this to turn into a computer science project. I see no reason to write a multi-language loader into Inkscape that can resolve everything and make one big happy application. I'll leave that project to the Mono guys.
I think that, we should allow plug-ins to be dependent on external libraries. And, we should provide a way to check versioning on those libraries, but we should not provide linking. If someone comes up with functionality that is useful for a large set of Inkscape extensions, they are welcome to publish that as a library in their language of choice, and other people can use it - infact, I'd promote people using libraries like SVG.pm and the such, I just don't want to do the handling of APIs and pulling everything together.
We do, however, need to provide an API for extensions to be able to touch much of the Inkscape internals to be useful, that is a must. And we must provide some way for extensions to use that functionality. I think this should be our focus.
So, I'm sorry to hijack this thread and bring it down to this point, but I think it is an important point to discuss and come to agreement on.
--Ted