It is not package manager per se but for CLI with R there is littler
There is some pre made script for 
installation presented in examples and script folder.
About packrat, it works well and system dependency is not an easy task. One face is that it is not always possible for a user to install linux dependencies on a server. I am curious if python pip can deal with that or not. 
It is often a two step process:
- Identify the system libraries an R needs
- Install them using the OS package manager
There is some tools and service to help with that like sysreqs and its sysreqs.
On some specific OS like debian, there is some precompiled available in the OS package manager, here apt-get.
If you find something, please share!