I was marinading some skirt steak and chicken parts today, and I remembered that my father always added breadcrumbs to his marinade for grilling chicken.
Why? Well, they help stabilize the oil/vinegar emulsion (even mustard, ketchup and syrup won't quite work at that volume). And they help keep it on the meat during cooking. If your fire is too hot, they may char a bit more, but you can usually control how far to go with that.
Having a partially opened bag of panko breadcrumbs, I added a cup or more to a couple of cups of marinade. The panko breadcrumbs seem to help stabilize the marinade even more than regular crumbs.
And, behold, it was very good.
Now I have to remember to make some Cornell chicken next week.....