First off, I'm sorry I haven't had a chance to test the current version of SVGSlice.
The external script type extension system is simple and powerful. It has many applications but I think we are trying to stretch it beyond comfort. I'd hate to see it made any more complex. Simplicity and the ability to communicate with external apps in a generic way are its coolest features.
IMHO a convenient slicing feature in Inkscape will be appreciated by the silent majority. But it is completely useless to package the files as an archive. That just isn't part of the workflow.
I've said this before, but I think a file selector autogui widget would come in handy in exactly this situation. SVGSlice could be an Effect. The user would be prompted by autogui to select an output directory. After that Inkscape would be done and SVGSlice could interactively prompt the user as to whether or not to replace files.
Thoughts?
Aaron Spike