I mean, it's possible to use some deep fake shenanigans to digitally recast him, right?

Or how about this...they take another year or whatever to reshoot with a completely different actor for the flash...

Photoshop him into Reverse Flash.

Oh Like Venom! Wait no

i still say they could easily fix this. have Barry go back in time to save his mother but just like Justice League he goes back too far, accidentally A-Train's he own pregnant mother and immediately disappears. 6 minute short. play it before Aquaman 2. problem solved!

too easy.

"Barry my son, I lied, your name is actually Hunter Soloman and also I'm from the future and so are you"

Make the Flash yellow in post, ez