I meant that if I were designing a general-purpose retain-mode GUI library or 3d engine from the ground up and wanted to incorporate his principles as much as possible, how could I do that? Maybe a retain-mode approach is just inherently (too?) complex?

Correct me if I'm wrong, but I think your answer is in reference to using such a library, and I can certainly see how my question implied that, so sorry for the confusion if this is the case. Thanks for your answer regardless.