Yeah the blackface in Tropic Thunder is very much in the text of the film. I seem to remember it being a direct parody of a Vietnam War movie where a white actor unironically played a black man, but I may be Mandela Effected because I can't find any references to this.

Mel Brooks playing an Indian Chief in a short scene in Blazing Saddles...doesn't really have room for it to be in the text, but given the movie has an overall theme of racism in Westerns I think the subtext at least could be there. Especially since this movie leans on, breaks, then demolishes and spills out through the fourth wall, it has that same "we're actors playing roles" mechanic that Tropic Thunder does. Slim Pickens even delivers the line "I'm working for Mel Brooks!"