I don't think it's quite that easy. There's plenty of people who have a bad trust rating here yet they are still able to do business without much of an issue. I'm not sure the change you are proposing would have any real effect.
As for the self proclaimed scambusters, I appreciate their work around here. It helps me when I'm managing signature campaigns and looking for users to enroll. Blindly following the DT is not really an issue IMO. The only people you see complain are mostly the ones that have actually been caught with doing something bad..
The trust system is constantly abused for political as well as likely organized criminal purposes. It provides cover for these people to abuse honest contributing members of the forum with impunity. The question is not if they help, it is at what cost? The cost is consistently driving away MANY new users who simply didn't understand the unwritten mob rules enforced here. The thief simply spends a few bucks on a new account and is back in minutes. Legitimate users burned this way don't come back, perpetually putting us in a feedback loop of driving away the decent user base while providing cover for the cons.
Blindly following the trust is a HUGE issue. There is no way to even know if the same person is truly in control of the account any more at the end of the day, and purporting otherwise is disingenuous and only harms the people it was designed to protect most, the newer users. It is at its best little more than a notification system for people to warn others of suspect behavior, and at worst a system of protecting organized crime and mobbing cliques.
"The only people you see complain are mostly the ones that have actually been caught with doing something bad.."
That sounds like something dirty cops say when some one tries to get the cop to follow the law too... the rules are for thee and not for me.