Brandon,
I just bought Larry's 4 burner first generation Summit. On my long list of "To Do's" is to disassemble the firebox and take the rust prone part to a sheet metal shop. While a good sheet metal person could make an exact replica in stainless steel, I think the cost would be very prohibitive. I am thinking more along the lines of having plates made with two holes for one half of a 4-burner or one third of a 6-burner. Make plates to bolt to the front and back side of the area that always rusts out. No, it won't last forever, but I think it would be a potentially cost-effective way to give your old Summit years more service. I also hope that the price could come down if made in a small run of identical parts. Then I could sell them at cost to other hobbyists. The first generation Summits are SO nice other than this very annoying - but also serious - problem.