It works, my job here is done.
Oh, except for:
-documentation (this is one i basically *need* to do)
-outputting real, physical instead of the symlinks i'm doing right now
-generate ebuild cache
-test loads and loads and loads of packages (help wanted)

Again, quickly a guide to use my project:
-Install layman from the kuroo overlay and g-cran from the science overlay
-Save the attached repositories.xml to /var/lib or whatever
-Add file:///var/lib/repositories.xml to "overlays" in /etc/layman/layman.cfg
-layman -a CRAN (or the two bioconductor repositories, which are in
repositories.xml as well)
-emerge -av dev-R/zoo (just one of the many packages in CRAN)

I spent some time helping wiktor prepare g-pear for g-common too, so
keep track of his work if you're interested in PEAR.

Have fun!