I agree with Flip and Timon the Great and DGF.
I mean, we already had a spam of pointless topics in the TLK sections just recently after the cleanup without offering an award for activity, and I assume that a requirement for the award would be thought-out posts, not random tiny spam posts. I mean we can all tell the difference between "I think Simba did this because <lots of reasons and explanations of opinions>" and "I hate Mufasa cos he's mean >C." I mean... it's kind of obvious who thought about what they posted and who didn't, and that kind of spam will appear from time to time regardless of any awards.
This one seems like it would be good. I mean, there are the fan fiction and fan art and the on topic RP sections as well as the movie specific discussions that are all TLK, and loads of people post actively in those TLK related boards, so I don't think it will be exclusive at all. I mean we have the typical crowd in the Kingdom, but we also have a bigger crowd in the Fandom. It only excludes people who never post about TLK. That isn't really many people considering we're all here for being fans of the movie(/s).
It's also good for those who aren't ardent Den posters because they can get an award for what they do now without having to be extremely well known and overly kind and whatnot. I love the Den, and do mostly post there, but posting in all sections from time to time really shows me there are important and great members all over the board, but usually it's just the Den crowd who get MoTM, and understandably so.
I see absolutely no reason why this should be a failure or why it won't work or anything like that. I think it's a great idea.