right now this is what my manifest files look like:
---------------------------------------------------------------------------------
name: mypackage
version: 0.1
description: A short description of the package
{dir} /path/to/destination/folder 0755
{dir} /path/to/configdir 0600
file1 /path/to/destination/folder/file1 0755
file2 /path/to/other/file/folder/file2 0644
file3 /path/to/config/file3 0600
---------------------------------------------------------------------------------

so what I was thinking is adding a line like
depends: extpkg otherpkg differentpkg

then, during the install process, before it installs the requested package, read that line and run the install function for each of those (which would recursively take care of any dependencies of those dependencies). but i have a feeling that might be oversimplifying things or ignoring potential pitfalls.

EDIT: now that i look at that manifest I realize i need to update my docs/manifest_example because this is totally not the current working format :P but it gets the point across.