I fully agree with your analysis and recommendation that "millets" need to be the default usage when talking about all the millets in general, and "millet" used when referring to one of the millets.
One of several things I've been thinking about is a kind of press package about the International Year of Millets. There are several considerations in preparing press packages, but one theme I
think will be useful for any guidelines for journalists writing in English will be encouragement to use the plural "millets" when referring to the generic category, and not the singular form "millet." The latter form may of course be appropriate when referring
to specific crops / foods, so clarity on what one is writing about, and how it might be (mis)read is central.
In support of this process, I began a couple of months ago to put together some "data" on articles which infortuitously mix the plural and singular forms in ways that can't but be confusing to
general readership.
A first attempt at presenting the latter, with comments, is in the form of a PowerPoint presentation, which is attached, in ppt & pdf formats.
Your feedback will be helpful and appreciated.
Thank you in advance, and best to all,
DO, EL, MI, US