I wonder why this wouldn't work:
Depends: libthing4 | libthing5 | libthing6
I personally would have just created a package for the software and
used dh_shlibdeps as per normal.
If that doesn't work and you actually want the libraries as
dependencies of a metapackage, I would not add a new field but just
add the right libraries to the ${shlibs:Depends} substvar.
--
bye,
pabs
http://wiki.debian.org/PaulWise