Okay yes, we know that Batman and Nightwing have a significant age gap between them, and that Ben Affleck is nearly a decade younger to Donnie Yen’s 53. That being said…it’s Donnie Yen. He doesn’t really seem to age, and as Rogue One and XXX: Return of Xander Cage have shown, he can still kick tons of ass at his age. He may as well be a superhero, just ignore the age thing as best you can.
Fans have been asking for the Walking Dead and Voltron star to play Nightwing for a while now. At this point, the DC Extended Universe should take any opportunities they can to gain goodwill, and this would certainly get people more interested in this movie. Lee is no stranger to comic book films, having starred in RED 2 and the GI Joe films in recent years. Plus, there was the Magnificent 7 reboot last year to show that he’s extra proficient in hand to hand weapons. If nothing else, he’d lend himself well to the fight scenes and acrobatics. Recent years for Dick Grayson have seen him being a James Bond type spy, going around the world and stopping the forces of evil. His solo movie likely won’t address that part of his life, but even so, there’s no denying that for any scene that requires him to don a tux or flirt with some lovely folks, Henney would certainly clean up.