There is the issue of external validity which I can't figure out. I appreciate any suggestion. Note the solution should not include empirical studies (only computer generated results).
It depends on what you mean with "external validity" . There are possibilities to calculate performance parameters of an MCDA such as Redundancy, Uniqueness and Separation capability during the process of defining and optimizing an MCDA. There is a platform called Determinator for developing DSSs (or MCDA) : www.determinator.wur.nl . The player is freely available, please contact me for the Developer. More explanation on these parameters can be found in the paper: http://dx.doi.org/10.5772/51362 .
Conference Paper VALUE DRIVEN DESIGN AND DECISION CONTROL IN COMPLEX SYSTEMS