I think it's a great idea but somehow I get the feeling our photo contest is already influenced by many more things than what's the best picture.
What people vote on in the POTM is really personal preference. If somebody has a really cool thing to show off it might get a lot of votes even if it may not be the best photo technically.
Remember when clownfish won the schooling fish category? It doesn't even have to match the theme of that month!
So to me POTM is already about which photo each voting member likes best rather than adhering to the topic or picking the best photograph from a technical standpoint.
It's what makes it so suprising and exciting. You never know

If SOTM doesn't make it as a contest you could always start a thread like John suggested encouraging people to post their favorite critters