Thee was this very old karting game "Wacky Wheels" which had running Zoo animals in small circuits <!-- s:) --><img src="{SMILIES_PATH}/icon_smile.gif" alt=":)" title="Smile" /><!-- s:) -->, it wasn't that bad and AFAIK the engine they used was a preliminary for the doom engine, so I think it can be a good idea for a gameplay mod, but I'm not sure how easy/difficult it would be to make this... <!-- s:? --><img src="{SMILIES_PATH}/icon_confused.gif" alt=":?" title="Confused" /><!-- s:? -->
In conclusion, I think it's a nice idea, hehe! <!-- s;) --><img src="{SMILIES_PATH}/icon_wink.gif" alt=";)" title="Wink" /><!-- s;) -->