Level 3 Referee
2- agree to an extent, especially when it comes to SFP. But with things like HB or a trip in which defender may or may not have touched the ball, think slow-mo helps
Slow-mo is valuable for determining many of the considerations for SFP like point of contact, and it helps to determine the body shape of the guilty party at the time of the contact. IMO, slow-motion replays should be used in conjunction with real-time in order to asses all of the considerations for SFP, of which speed and force are but two.
4- this one is all well and good, but will lead to more inconsistencies as common sense will differ from person to person
Yeah, this isn't even a serious suggestion. Whenever people say they want the referee to use common sense, they mean they want to referee to do things which they agree with.