"It's nice to stay on a relatively stable release and NOT have major upheavals in the entire platform so often, but it would be powerful to couple that stability with the ability to easily update key componentry in just one or two areas."
IMHO the only way to achieve this goal is to limit the number of packages you support in the official distro. Ubuntu did something like this with debian. Whereas debian has thousands of packages to support across multiple platforms ubuntu has a much reduced set and only supports intel and PPC.
Everything else is still available but on unsupported repositories.
Perhaps something similar could be done with RHEL or Fedora.