Trying to effect an arrest with 2 people surrounded by 20 is a sketchy proposition.

I've been saying for years that they need to rig up the police vehicles that have the potential to be used in urban areas (where they might be surrounded) with a full-frame taser rig, similar to what one might do with an electric fence. Got a bunch of miscreants attempting to stop the vehicle by laying hands on it? Discharge that sucker and I guarantee you they'll let go of it and back the hell off, pronto.

I'm also all for rigging them up with on-board tear-gas deployment and any other number of anti-riot capabilities that can be set up on a standard car.