That ash pan doesn't look deep enough to hold fire bricks but maybe placing some ceramic tiles in there would attenuate that heat enough so it lessens the likelihood of burning out the pan - maybe???
Fire bricks came to mind also but pan is not deep enough. Tiles maybe?? It's going to my bro's and I think he's going to reinforce it with a thicker gauage scrap metal at his shop. He's got some ideas on making it more solid. Honestly, after cooking on it yesterday you'll be fine leaving it alone but def wouldn't hurt reinforcing it.