I loved when we could bred pets. Dog fighting might be a but to much, but why don't bring them back and race them?
Dog racing, horse racing, camel racing, etc.
Also opens new dimensions to several aspects in the game. You can breed, trade and race them. You could gamble on the races (would be cool for racing too). And you might connect some company specials to it.
Just for your consideration.
My time is limited, but if you like the idea and want to brainstorm, count me in.