we should be able to use them in free for all or free teams or infection or teammdeathmatch. in domination the dog bit you if you got toooo close but what if you could buy up to 3 to 5 dogs that were faster and more powerful than the one in domination and could find all players on the map and try to get you some kills 
. But you could kill them and since the dont shoot take two times longer to kill than a regular player. 
You could buy them in the market in the shape of dog bones and the would appear where you dropped them. cost= 20-30 points
i think this is a cute idea 
keep on....
and I could take them to walk every day.