Ok, I can see a theme developing (sorry) here.
From what I'm seeing, I think it is going to be very difficult to judge film against digital to everybody's satisfaction so, and I'll be honest, I'm not sure what the solution is. I'd hate to lose the film photographers from the competition but do you think it'll be better stripped out and operated as a completely separate Film POTY?
I don't think (or at least I hope) that nobody who's shooting film actually wants any kind of special treatment because they're (it'd be we're but I don't feel comfortable helping out with the running AND entering the comp. - it's just too messy.) shooting on film. We shoot on film because that's what we enjoy working with, and, certainly speaking for myself, because I like the look that I get from working with film.
My suggestion would be a sort of 2 fold approach...
1) Remind the judges that if something is shot in B&W on film, it's almost 100% guaranteed to be a stylistic choice made at the start of the project, NOT a conversion to rescue an image that was shot with the wrong white-balance or in unfortunate mixed lighting conditions.
2) Run the film entries as part of the normal competition - so if they get in the top 10 they get points for the main competition as normal. Plus, get one or more of the judges to at least rank the top 10 film shots, so that everyone who shoots on film will have a chance of getting points for the FPOTY leaderboard. It always seemed rather tough that there could be half a dozen film shots and no points accrued - certainly a reason where you could expect a drop off in numbers entering on film.
As to the issue of judges "keeping to the brief" - well - it's a tough one... The themes/topics for this year are deliberately a little less prescriptive, partly to encourage a wider entry and partly to encourage people thinking "outside the box" a little. I know that in the 3.5 years I entered the competition there were months when I looked at the subject and just went "well, that's me screwed then" - then went away pulled out my thesaurus, did a little thinking about things and came up with a twist on the title that would work for me... sometimes it worked and I got votes/points, often it didn't and I shrugged my shoulders and thought "well, at least I tried". Frankly, I'd sooner look at something thats had an imaginative and creative spin put onto the theme than a whole row of same old, same old...
The judges are on a thankless task - if they're too regimented and prescriptive in their marking, people spit their dummy out and say they're dismissing anything creatively interpreted - if they embrace a more open minded approach, people say "that wasn't to the spec." - At the end of the day, they're all people who've actually won the POTY in the past, in most cases iirc back when the comp. was "peer voted", so they've been kind of appointed by the membership already...
Ultimately, they are the judges, their decision is their decision, and by entering the comp. you're putting yourself up for judging by them - and by spitting your dummy over their decisons, you're no better than someone who replys to negative crit. with the old chestnut "but the client liked them, so thats all that matters" If you're not prepared to accept the judges decision, then maybe entering the competition isn't for you... But, IMO you'd be missing out, because I know, the discpline of entering the competition with the best photo I could possibly take every month improved my technique noticeably, and, perhaps more importantly, improved my ability to "think about" my work to a huge degree.