He's appeared on Flash as his old character live action, so it's possible. I'd love to see the Trickster show up as a mentor for Non-Joker(tm) on Gotham. They utterly wasted the Scarecrow's dad's potential when he wasn't played by Jeffrey Combs, even though Jeffrey Combs shows up in a minor role as the Toymaker's goon. The Toymaker isn't even a part of the Batman Rogue's Gallery.