I think the right way to do it is remove the version number and have anaconda depend on just the libblockdev-plugins-all package since it doesn't really care what the specific version is. blivet should enforce the specific version that it needs by a dependency on the main package, which I think will cause the correct plugin versions to be pulled in. No need for subpackages.
How should that happen? The ``libblockdev`` (main) package doesn't require the plugins and thus cannot require any specific version(s).