I found a solution on my own. Finally ran across the webpages of Michael Friendly (http://www.datavis.ca/) where one can search for a macro that makes a "trilinear plot" or triplot (Visualizing Categorical Data: triplot - Macro for trilinear plots). I'd still appreciate any other ideas and, being this functionality is already incorporated into JMP, I still hope for when it'll become one of the ODS graph templates available in SAS. Until then, this solution is working fine for me and I hope the information might help any others with similar needs.
Dave
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