On Debian Wheezy (testing) and Ubuntu 11.10 and later releases for both, the "ifupdown" program can now take a "source" directive that reads interface stanzas from a specified file.
From the interfaces(5) man page (Ubuntu 11.10):
This will require that users have their /etc/network/interfaces configuration set up to include a source line with the files they wish to include. This could be done with a wildcard, per the man page entry, e.g. "source interfaces.d/*". Such a thing could be handled with Chef::Util::FileEdit, but that seems heavy-handed.
The current ifconfig provider is RHEL specific. It would need to be moved to a new provider and the Chef::Platform default provider for RHEL-family set to use the new name (I propose redhat). Then this new provider would be appropriately named debian, and the default provider on Debian/Ubuntu.
The main issue I see with that implementation is that the Chef::Platform version specification does not allow setting "versions greater than..."
Debian bug resolving the request to add this feature (source directive):