I just think it would be terrible for the sport, it would turn it into a complete clown show. I think it would be bad for publicity as well, I don't want to get back to that whole "human cockfighting" attitude.
But, to dovetail this into betting, it might make some for some interesting bets, possibly more value on dogs due to the variance it might create.
Still though, I don't know why some people are actually suggesting they should be legal, it's just stupid.