No one knew about transfats in those days and in fact margarine was prescribed for people with heart problems, so that they would avoid butter.
I think using grapeseed oil (which has a high burning point) and then adding a small amount of clarified butter (ghee) will be a good alternative. The idea for this mix come from Gray Kunz, who is a highly regarded chef (although he was not referring to Creole or Cajun cooking.)
PP explains in LA Kitchen and on his tv shows he likes it for higher burning point when sauteing his seasonings, then finishes a sauce with a swirl of butter.
Caveat: I find his original heat and salt levels to be way over the top. I cut the cayenne in half in every recipe or homemade spice mix and find it sufficiently piquante.