Hi,
I've been testing in advance to make mass rebuilds changing macros and the results are pretty good (I mean x86_64 f20, f21 + grsecurity custom kernels). It is clear that we will find regressions, we just have to start and test it.. It is an important and necessary change.
If anyone is interested would be important to look at uClibc and musl (Alpine Linux is based in this one).
Note that other distributions are doing an excellent job in hardened profiles like Gentoo or more actual OpenSuSe Gardened:
We have to work on mitigation rather than patching and trust not responsible maintainers for some packages. This includes thinking seriously about to have a kernel with grsecurity patches.
Cheers,