An au idea: John and Paul are 19th centuary artists with very different styles. They were even thought to be rivals. Then one day stuart comes across a chest in a descendant of Paul's home with paintings and letters from John. he quickly puzzles out that they were in fact, lovers. And what was once thought to be a self portrait of Paul, was actually done by John - making people realise how skilled he was and how much he adored his lover :)
ohhh my GOD. i’m cryin, this is amazingly perfect.
like they would have kept the idea of being rivals going too, old letters also exist of them exchanging snappy correspondence and ones sent to other people at the time make mention too (after some time, paul goes off to start running a small farm, and he tells someone else in a letter, “which i fear i will be as adept at as john lennon is at painting anything of substance”), but john is just as bad and dismisses paul’s stuff (could he be anything but some kind of landscape painter? tho get george involved and he’d do that too) as the sort of nice, pleasant things that will decorate the parlors of england’s old biddies for years to come.
and then of course they’re exchanging these secret letters all the time, including little hidden details in all their work that actually reference the other. john’s known for doing more abstract art but can commit to realism too, one of the times that he does is for that portrait of paul and so different from the rest of his stuff that no one (at the time) thinks twice about it. but then it’s referenced in one of those letters and oh…OK, i could prattle on about this for a while, but seriously, YES (!!!!)