Manuel, In RPM the only restriction on 'version' is that it must be made of alphanumeric or period. Ref: http://www.rpm.org/max-rpm-snapshot/s1-rpm-inside-tags.html Just for a small test I ran a perfectly legal version pattern, that is allowable in distros other than Fedora, through your patch logic.
version = A2 release = 0_rc1 version-release = A2-0_rc1 # this is what we expected to see version-release = -0.0_rc1.A2 # this is what we get instead as strings are modified by patch logic
This is why I suggest that you make an extension module triggered by a commandline option so there are no restrictions or unexpected side-effects introduced to non-Fedora distro users. Right now, I'm a big -1 on the patch. If it would be made as an extension triggered by commandline option then I would support it.