utility to downgrade a package with its dependencies?

[Vincent Lefevre <vincent@vinc17.net>]

For Debian/unstable:

Does there exist a utility to downgrade a package with its
dependencies and reverse-dependencies? The old packages would
be taken from /var/cache/apt/archives, and the tool should be
able to find automatically which packages/versions are needed
to satisfy all the dependencies (with minimum change) and
should be able to handle virtual packages.

Doing that manually is tedious...

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Vincent Lefèvre <vincent@vinc17.net> - Web: <http://www.vinc17.net/>
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Work: CR INRIA - computer arithmetic / Arénaire project (LIP, ENS-Lyon)