I'm almost of the mindset that just having userspace apps as lxc containers with everything an app needs may be better for the most-used applications...
Given how relatively cheap even fairly big SSDs are, is it really worth the storage savings for your browser to share a couple .so files with your mp3 player?
I actually like how PC-BSD pbi packages work... given the number of times solutions have been made to work around the issue and reduce space... I'm not sure it's always worth it. At least not in the desktop space.