One option is in relation to reputation. I have no problem with this, at all. I think this is a good addition save for the fact that it has a lessened effect on all the previous genuine negative feedback.

Flags are inherently flawed in the fact that the victim of a scam must flag the user.

Innocent until proven guilty, sure. But with this one it is unflagged until victim proves scammer guilty. If no victim acts on the flag, then nothing is done. You are not allowed to flag without first being scammed.