I think a two rank system would be good.
Someone currently in a dispute should have DO NOT TRADE and should limit most of the forums except the dispute section. this will prevent them from trading while in a dispute
TRADE WITH CAUTION should be used for people who previously scammed and refunded @Orange. or are suspicious. This person will still be allowed to trade and use the forums but the other person will know it COULD be risky.
Let it me know what you guys think