You can use a disc over charcoal. It's not as easy to regulate temps so be careful if you plan on deep frying. It would be perfectly fine for fajitas, stir fry, breakfast scrambles etc...
You'll also want to figure out a set up for setting the disc on. You could put it on the cooking grate but it will want to flop around. You could remove the grate but you don't want it directly on the coals, nor do you want to block air flow from the top. Which could happen if the disc was resting on the rim of
the kettle.