I think fail-muggers should be insta PK'd on the spot since the victim never got the time to get their revenge and kill them. Fail-muggers are essentially by passing a PK and only getting a ban instead.
Now, about PK'ing the main too, I thought it was ridiculous at first, but honestly that would make muggings a lot more high risk high reward more fearRP , consequential and more exciting tbh. Tired of pussies not doing it on their main account. Come risk your life on the char you have $5 million+ on , not some random minge char with an old char ID and some money to make it look like they "value their life".
And like Bananaguy23 said, the biggest issue by far is going to be new/semi-experienced players. They will be able to use the excuse of saying "Oh I'm new I didn't know." which may or may not be true.
Either way +1.