In camp I normally use either a 1' x 2' piece of seasoned 1/4 inch thick sheet metal, a section I cut from a shelf I took out of an old oven (cut to make it smaller), a cast pan, or my dutch oven. I normally just prop them over the coals on rocks.
I've considered a tripod or spit as a way to adjust temperature and make cooking easier, but so far I've just been getting by with adjusting the amount of coals under my cooking surface.
If I build the fire ring I like to make a keyhole shape and use the smaller end as my cooking area and the larger side for the main fire. When I get ready to cook I pull the coals into the smaller area and adjust the temperature that way.
As I think of it, I'm not sure a tripod or spit would work for me as I'm still going to want to use a frying surface or the dutch oven as an oven for most of my meals and both the tripod and the spit would be in my way for the majority of my cooking.
Still might build one to try out though - I could be wrong and end up thinking it's the best thing ever.
I'm thinking I could build a tripod out of rebar with a little blacksmithing. Or even simpler, I could hook 3 rebar poles together with a single metal ring (somewhat like I would tie wood poles together for a tripod). This is going to require some experimentation.
goody, goody, goody (I like building and trying things out)