I'm enjoying a Merlin rewatch myself, albeit at a slower pace.

the thing that struck me most was that Arthur was far less of an idiot than I'd remembered.

He thinks for himself far earlier in the series that I recollected.

I'm with you on redemption stories. In every fandom, without fail, fans have a marvellous ability to forget all the really horrible things done by their favourite characters.

If you write the story you describe , I'll read it!