In its letter, signed by chairman Kieran Quinn, the MBA explains that "such a symbol would brand all structured securities as a single asset category, despite the fact that different structured securities exhibit markedly different performance characteristics (e.g. CMBS, RMBS, and securities backed by credit card debt or automotive loans).

"This could spawn greater investor confusion because a wide variety of securities would be lumped into an equally broad investment category. Consequently, the performance of a single type of structured security might be attributed inaccurately to other structured security products due to their shared product identifier for structured securities would cause disruption and informational disparities in the securities market."

Duel ratings, Denney adds, would imply that real estate-backed asset securities are more risky than other securities. "One goal is to get investors willing to buy CMBS again--we think this proposal would in fact reinforce the current retreat [from these securities] in the market," Denney says.

This is the first of three public comment periods before the SEC makes its decision. While its duel-track proposal is a radical realignment of the current system, there is a good chance the agency will reconsider, especially after the comment periods are through. "There is not much support for the duel-track system," Denney says. "Regulators routinely make significant changes from a proposed rule to a final rule. When that happens it means the process is working."