I submitted a Change for wrangling today, but I'm also putting it here
for discussion:
https://fedoraproject.org/wiki/Changes/OnDemandSideTags
This is intended to be an alternative to modularity, in the sense
that it allows some rpms to be built against older or newer versions
of dependencies, but the details of this process are invisible for
end users, who get only normal rpms.
The text is too long to paste here, so please take a look on the wiki.
I'm especially interested in feedback if this would work for *your*
use case and make *your* life easier.
Zbyszek