They say an image is worth 1000 words, so here's a (9 Legendary, probs) male laying down next to a (level 1) female tiger. These are both adult tigers.
I can't imagine it would be so hard as to implement a slight model shift that simply enlarges the animal based on level? It might be difficult, but the outcome would be absolutely amazing and completely worth the effort. With antler'd species you can visually immediately tell the difference in levels between two side by side animals, not so for non-antlered species. This single disparity greatly diminishes the fun of hunting non-antler'd species. When you see those enormous racks there's a huge dopamine hit as you anticipate getting a diamond. The tiger/lion/etc. hunts do not have this at all, or it is greatly diminished.