Adding that text to the packaging guidelines seems like a sensible idea, yep. You'd have to propose it in an FPC ticket, that's the procedure for packaging guideline changes IIRC.
After discussing this on the packaging mailing list, it seems we don't need any modifications of the packaging guidelines: https://lists.fedoraproject.org/archives/list/packaging%40lists.fedoraprojec...
After further consideration, I've also created a FESCo ticket to officially approve this: https://fedorahosted.org/fesco/ticket/1534