If I understand correctly, Flamenco has the ability to load all linked libraries in all the slave machines recursively and without the need to pack your blend file or alter it in any way, which I find simply amazing (though I haven't tried it yet). Do you plan to implement such a feature as well?
To give you some context, in my daily job (as well as most if not all movie-making pipelines), packing a file at render time is not an option because it would break the asset editing process. Being able to edit linked assets, materials and lights after rendering is crucial, since rendering is precisely the only way to tell what should be edited (at least for materials and lighting).
If I pack a file, render an image and then perform some changes on the assets, these changes won't propagate in other files of a larger project as they should, since nothing is linked anymore.