Yes, rental of approved fire pits would make a lot of sense! A nearby state park at the shore doesn't have fire rings at the sites and requires you to bring your own, but they do rent them at the camp office as well.
I know storage of them would be an issue, but we have one that folds down into a little case and is "disney legal" with a solid cover and screen sides.
Or, they could just add legal fire pits, especially at the premium sites. I'm thinking a lot more people would appreciate a fire pit and if given a choice, would choose one over a grill.