What if, you could tame any animal to be your pet/mount? It could help you fight enemies and it could help in finding certain items (e.g. it could sniff out a certain plant or something) and possibly let you ride it(sort of like the plane and the boats) to get to places quicker.
I am rubbish at modding and scripting, however i am rather good at making maps(though i rely on the 'fill map randomly' tool all the time.) so i would be glad to help with this if someone actually tries it.
And yes, i know it would be very complicated. But, think of it like this, you will be adding a whole new aspect to the game. A whole new way of playing it.
Well? What do you think?