It would be useful if we could take debconf-get-selections output, parse
it, and plug that into a debconf db file besides the system default.

For example, when administering many systems it is expedient to preload
debconf, and it is very useful to use the File, DirTree, or
PackageDir drivers in combination with the Stack meta-driver.

Preseeding would be made even easier if the workflow could look
something like this:
debconf-get-selections | grep -E '^mypackage' | debconf-set-selections
-f mycustomdb.dat

So it would be nice to see a command line option for
debconf-set-selections to customize destination output.