Hey,
Taste wise, it's pretty close to French mayonnaise.
I would take the french recipe (whisk method):
Classic Mayonnaise Recipes | Ricardo
To be as close to the taste as humanly possible without all the chem stuff, I would prefer the White wine vinegar, cut down on pepper, replace the dry mustard with half the quantity of Dijon mustard.
Maybe add a pinch of sugar at the end (because let's face it, there's always sugar somewhere in a Macdonald's recipe).
You should be pretty much there.