I would consider that a spectacularly bad idea for a family dog - especially the biting bit.
The reason is that if you reward dogs for a behaviour they tend to use it more, even if you haven't asked them to. For instance, most dogs learn early on to 'sit' in return for a treat. If you have a bit of food the dog wants, it's common for a dog to try sitting and looking hopeful even though you haven't asked it to, in the hope that treats will be forthcoming. Occasionally mine does this to other dog walkers who have treats in the park. It's completely harmless but an example that dogs will do things they have been taught without being asked.
(On a side note, you should never tell a dog off for growling - it's often a final warning before a bite, and you really want that final warning!)
Police dogs (general purpose ones, often Belgian Malinois, not sniffer dogs) are taught to bite on command, but they are also taught a 'release' command. Unfortunately they can do quite a bit of damage in the meantime, and they aren't terribly good at telling the difference between uniformed police and criminals - police officers will tend to vacate before the dogs are released. It can go wrong from time to time; there was an elderly woman killed by one in Middlesbrough a few years back, and it was far from the first time the dog had gone too far in biting. If the police cannot reliably train dogs to bite the right thing and only the right thing, then Joe public definitely can't.
There are some online who will claim to sell 'personal protection dogs' and make out the dog has the judgement to tell the difference between a burglar and the postman. It doesn't. It's like giving a 3 year old a loaded gun and a job in security and asking them to make judgement decisions about when to shoot. It's spectacularly dangerous. Thankfully these dangerous people are few and far between, but their target market is clearly the criminal fraternity. This sort of thing - good luck getting the dog to tell the difference between little Johnny being attacked and little Johnny play fighting with little Tommy. www.instagram.com/reel/CoBTpc3gGzY/?igshid=YmMyMTA2M2Y=