As I asked in an earlier message, what is your goal?
If it is to provide a template for simplify the process of creating
packages for upload to the main archive, then the direction you're
currently heading is fine--presumably the maintainer is sufficiently
clued to deal with the occasional corner-cases (such as epochs,
replacing CORE scripts in /usr/bin, etc).
If it is to provide a binary package for each and every CPAN module,
then I would stand by my suggestion above: choose a disjoint namespace
and install to /usr/local. There may well be some overlap b/w some
cases of cpan-foo and lib-foo-perl, but that's not terribly important
so
long as cpan-* is self-consistent (a couple of redundant Debian
packages
is hardly a huge overhead).
If you intend to tackle both tasks, then perhaps you need to provide a
switch to choose the appropriate behaviour.