I'm not sure I understand why there would be a limit to the number of logic levels. That would make it difficult to create complex circuits. There naturally arises a maximum number of MOSFETs that can be connected back-to-back without being connected to the rails, such as in a transmission gate mux architecture. But that's just a consequence of signal attenuation, and there'd be no associated DRC, since it would be up to the designer's discretion.