I really hate the ‘tiny dogs bite too!’ that always gets trotted out.
Look, if there is a dog on the rampage running towards you in a park. No one else around. Are you really telling me you’d be just as scared of a chihuahua than a xxxl bully pitbull?
Jack russels/chihuahuas may be able to get a lucky bite in if they catch you off guard and you are already on the floor (so in a home environment).
But the bigger dog is most likely going to kill you if it wants to.
Perhaps a two pronged approach. Anyone can own a small dog, but need a licence which shows you have the ability to train them to a decent enough standard.
And requiring a special working dog licence for any dog classed as large and up. No one else can have one. Most of those types of dogs should be working to live happy fulfilled lives anyway, not shoved into a terraced house and only walked (if it’s bloody lucky) for half an hour a day.