Hi @cochetti,
Thanks for this feedback. As a former government contractor working on GFEs, I feel your pain. packrat only depends on tools and utils (part of a base R install), so you should be able to install without the suggested packages. This stack overflow post has some nice information on how that works. There may be some functionality you can't use, but install should work ok.
On the more general topic of package management, you might find https://environments.rstudio.com helpful in terms thinking about package management strategies.
Your use case is exactly why we developed RStudio Package Manager, which can really help with R package and system dependency management in validated/air-gapped environments. Unfortunately, it sounds like you have limited ability to do any sort of acquisition, but you might find the features interesting to know about.