Description of problem:
I do lot of builds with mock. If machine is powerful enough I would like to run multiple builds (as some take hours while other take just minutes).
Mock runs in /var/lib/mock/root/ which limits myself to just one copy at time. If I want another one I have to tweak configuration to create second rootfs from scratch. And do it for each package and clean after.
Multiple copies of mock run without interfering each other (they may wait during yum package updates).
I came from Debian and used pbuilder a lot. There you have tarball with basic chroot which is unpacked into /var/cache/pbuilder/build/RANDOMNAME/ and then populated with build dependencies and removed after build.
I think you may need --uniqueext=text option for mock, it adds a suffix to the buildroot toplevel directory making it unique without changing any config.
Are you looking for mockchain?
Closing per #1 and #2. There is nothing to do.