dev-libs/c-stdaux and the other libraries in that family are currently used as subprojects if the packages aren't installed. Please add dependencies on them. Some remaining ones may need packaging though.
c-stdaux seems like a particularly bad example to use: it is composed of of 5 header files. What is the point in un-bundling it?
I was really just naming it because I noticed the suite is now partially packaged. The real motivating example is bug 919100.
It does seem bad to automatically use system files though. I'll look into it.
It looks like he's doing versioned releases for all projects, so packaging them is feasible.