Are you saying this from strictly the “max gamut” perspective, or are you including consistency/repeatability, smoothness of gradients, etc. Just curious. I don’t doubt that great results are possible through methods you’ve outlined, likewise GMG can yield very good results, and offers useful gamut mapping options for contrast and neutrality.
Another avenue of discussion is the profile creation package used by the original poster. I’ve found that RGB profiles generated by Monaco Profile have been superior in terms of saturation and gray balance to profiles generated from ProfileMaker…but this is perhaps also subjective.