JD writes:
A user process (such as yum), even with root privs, CANNOT JUMP OUT OF THE BOUNDARIES OF IT'S ROOT, NAMELY (for example) /mnt/f15
Umm, that's not true. The chroot(2) man page has a nice explanation of how a root userid can trivially escape a chroot jail.
So there is no danger that yum executed within a chrooted environment will affect the enclosing host's yum database (in this case F14).
Nope, that's definitely possible.