How about ECN-2 film? Kodak does prescribe a stabilizer (Kodak Stabilizer Additive) in final rinse, but adds that in case of biological growth Proxel GXL may be added. This suggests that Kodak stabilizer additive is not formaldehyde-based and its role is only to protect dyes against reaction with colour couplers.
Photo Engineer wrote in the beginning that only recent C-41 films received a treatment against dye-coupler reaction, so I guess a stabilizer is a must in ECN-2, too (if longevity of the negative is needed).
Also I wonder if cross process of C-41 film with CD-3 based developer affects their dye stability. After all CD-3 creates slightly different molecule with a colour coupler than CD-4 does...