Now this one is a bit unscientific, but it's really simple to impliment. I was thinking about the question of "what is your best trophy" and it made me realize that, with trophy ratings ranging from animals that score diamond rating just above 6, to ones that have to score in the hundreds, there is no way to compare trophies of different species.
So I came up with "Absolute rating". Basically what you do is you take the max trophy rating of an animal, and then you render the current rating as a percentage of that, it wouldn't replace the trophy rating system, but it could be implimented alongside it so you can finally know whether that diamond jackrabbit you bagged is comparable to the diamond elk that your buddy has in his lodge!