That's what reasoning models are for. You can get most of the benefit by saying an answer once in the reasoning section, because then it can read over it when it outputs it again in the answer section.
It could also have a "delete and revise" token, though you'd have to figure out how to teach it to get used.
Given how badly most models degrade once reaching a particular context size (any whitepapers on this welcome), reasoning does seem like quick hack, instead of a thought out architecture.
It could also have a "delete and revise" token, though you'd have to figure out how to teach it to get used.