Interesting idea. One idea to add on to this is that the charring and burning occurs at faster rates at higher temperatures. For example, at 600°C, it would burn and char at the pace wood currently burns at, but at say, 9000°C, it burn completely about a second.
That might be a part of realistic heat/latent heat feature
I think you are suggesting something similar to coal when heated, but now it's just wood turning black from heat or flame. I like the idea, and it *should* be easy to implement. :)
I had intended the different burn speeds to be optional, as in it doesn't have to be put in the game, but if it goes get put in, it should be a part of realistic heat. The charring effect on wood doesn't affect saves in any way and would be a part of both the current heat system and the realistic heat system.