I think it would be a good idea if Blender was left out of the package and the package was posted as an addon to Blender. If you think about it, most of the people who would use it already have Blender, so to include it would be pointless.
I would however include as many plugins and python scripts as possible. It’s just too hard to find a good site that has all the really usefull plugins and scripts, so having them in one downloadable package is a good idea.
As for including BMRT and Lightflow, go for it. It’s always a good idea to have alternate rendering abilities. A good library of textures wouldn’t hurt either, perhaps gather the “best of the best” from around the web to include in the package.
The one thing I would highly stress in undergoing this project is documentation. Someone should setup a help file with documentation for all of the plugins, scripts, python use, and how to use the alternate rendering tools with Blender. Otherwise, what we wind up with is a package of hundreds of files which no one knows precisely what they do.
Overall I think this package idea has good potential. Since Blender comes in a very basic form with no extras, it would help people to build on what they already have. Every other 3D package out there has a large amount of pre-packaged plugins, textures, tutorials and other such items, so this post-package addon for Blender would simply provide people with what NaN didn’t give us to begin with.