FWIW, has anyone considered a fully ceramic grate?

One approach would be to bond pre-made ceramic rods with an ordinary
pottery clay, which could be fired as an assembly, then moved as a unit.

Another would be to cast/mould a grate-like assembly in a sheet, dry, fire,
glaze, and use it both as the heat diffuser and as a food grill in a gas-
fired grill (or charcoal).

'Tis hardly metalworking, but metals don't usually hold up well in that
environment.

LLoyd