How to add DKIM support for netqmail in Gentoo?

How to add DKIM support for netqmail in Gentoo?

I want to add DKIM support for netqmail in Gentoo Linux. It looks like
there are many ways to implement this but I didn't see good enough
solution yet.
Some solutions use wrapper for qmail-remote and recommend to rename real
qmail-remote to qmail-remote.orig - I don't like to do this to avoid
renaming it each time I'll re-emerge netqmail.
Next solutions try to support both DomainKeys and DKIM, and require both
libdomainkeys and libdkim - problem is libdomainkeys was removed from
Gentoo's portage - see bug https://bugs.gentoo.org/show_bug.cgi?id=391127
Last solutions doesn't looks compatible with netqmail.
I'm interested mostly in signing outgoing emails (in hope my emails won't
be trashed to spam folder by gmail anymore) than in checking incoming
emails, thus DKIM-only outgoing-only solution should be enough (but, of
course, I'd prefer to have more complete solution if possible).
Is there are any ways to implement this in less intrusive way (ideally -
by adding single patch to netqmail package)?