Antony Starr is 40. That means the movie, for him, would need to be made right about now. But for Amell and Clare, who are both 34, there's a few years to go before age becomes a factor. As for the rest of the cast, I've made several posts about what I thought about actors for those roles. Only an actress for the role of Susie Quinn needs to be found.
But if Amell, Clare, or Starr were to be cast as Trent Smith, I'd be cool with that. Yeah, I've been partial to Dustin Clare, having been swayed by his performance in Spartacus, but any one of these actors would fit the part, going by looks and the way they fight on screen. Sure, Amell is a bit too tall, but movie magic could fix that, no problem. Heck, if they can make the actors in The Hobbit look like dwarves, then that proves it.
Check out these photos. Each one fits my vision of Trent Smith. Which one would you prefer?