Many people can (and do) use R without building additional packages.

If you added system.devel, many R packages still wouldn't build without further packages installed. Where does it end, install every package that an R package needs to compile as well?

In saying that, there is certainly a need for the information to be available for users. My thinking is towards the future 'Help Center' as the solution rather than overloading it with rundeps.

As soon as you want to create/use more advanced graphics and methods you need to use R packages like ggplot2 and thus compile them before. system.devel is probably overkill, but as gcc and gcc-fortran are installed along the RStudio package, make should be as well. And maybe also the R base package itself for a little bit more convenience.

as gcc and gcc-fortran are installed along the RStudio package, make should be as well.

The reason gfortran (and therefore gcc) are installed with R is because they're required for R to run

And maybe also the R base package itself for a little bit more convenience.

Ahhh yeah, definitely should be installed with it!