This is from the updated USTR NAFTA negotiating objectives:
Dispute settlement: "Provide mechanisms for ensuring that the Parties retain control of disputes and can address situations when a panel has clearly erred in its assessment of the facts or the obligations that apply."
One way to address panel errors would be some sort of appellate review mechanism ... oh, right, never mind.
So how about this instead. There could be a formal mechanism under which parties can, in response to a panel ruling, register a specific objection to a panel's interpretation or application of a legal obligation, and propose an amendment (Article 2202) or an interpretation by the Free Trade Commission (Article 2001) in response. The other NAFTA parties would be required to participate in meetings to discuss the proposals.
This doesn't guarantee a reversal of the panel's approach for future cases, but it encourages parties to pursue their concerns by establishing a process to discuss them.