I've had a related idea for a while now.

Instead of how LLMs operate by taking the current text and taking the most likely next token, you take your full text and use an LLM to find the likeliness/rank of each token. I'd imagine this creates a heatmap that shows which parts are the most 'surprising'.

You wouldn't catch all misspelling, but it could be very useful information to find what flows and what doesn't - or perhaps explicitly go looking for something out of the norm to capture attention.