Steel isn't particularly good with an intense heat source directly below as in the BS. It's way too conductive. You could do it but you'd have to run the gas really low, and I don't know what you would gain. If you are trying to replicate your home kitchen oven outside for some reason maybe? With steel you would lose the high-temp capabilities of the BS.
There are a few posts on baking in a BGE, but it's really not a very good set-up for pizza. Steel will be even a bigger problem in a BGE because it's heat balance is terrible to start with. Even with stone, there is too much bottom heat and not enough top heat. Steel will make that way worse. In a BS, a large amount of the heat from the burner is directed around the stone and back onto the top of the pizza. The BS operates largely with forced convection for top heat which make this possible. You don't have that in the BGE.