The CW's superhero universe changed in a big way last spring when the Season 2 finale of The Flash sent Barry racing back in time to kick off the epic Flashpoint story of DC Comics fame. The Scarlet Speedster changed the timeline when he stopped his mom's murder, which meant that nearly two decades of history had to be rewritten. Those changes are affecting Arrow as well as _The Flash, as _John Diggle's baby daughter Sara was recently erased on the latter series and replaced by a baby boy. David Ramsey had this to say about how his character will respond to the _Flashpoint_ switcheroo of his kids, noting he'd respond:
Much more compassionately than you might think. Diggle can't miss anything he's never had and 'Flashpoint' changes history --- it changes his history directly --- so he never can really miss Baby Sara anymore, because he never had her, but he is concerned about Barry. Barry's actions were reckless, and with all that power, being reckless --- to someone as disciplined as Diggle --- comes as a shock.
Not everybody was happy with the fact that Arrow used Flashpoint to replace a one baby with a baby of another gender, but it makes sense that Diggle wouldn't be overly upset at the absence of Baby Sara and her adorable reactions to the superhero shenanigans around her. He can't mourn the loss of his daughter because she never existed, and we have no reason to believe that he loves John Jr. any differently than he loved Sara.
There's definitely precedent to the idea that Diggle as a military man wouldn't react well to the knowledge that Barry used his superpowers for a selfish goal that affected countless lives in ways that haven't even all been revealed yet. In fact, one of the things that Oliver and Diggle have always had in common has been their belief in the importance of discipline when it comes to fighting bad guys. Even if he can't be appalled that Barry cost him his daughter, he can certainly be appalled that Barry was so reckless with his abilities.
David Ramsey's reveal to ComicBook.com that Diggle will have a somewhat compassionate response to Barry's actions is a sign that Arrow will take the time to address what happened with Flashpoint rather than just use Flashpoint as an excuse to set up Connor Hawke without taking the time to write Lyla through another pregnancy. Most of the conflicts that Barry has faced over on The Flash have either been resolved quickly or occurred relatively recently in the timeline. It's possible that Diggle's perspective as a man whose life was fundamentally changed will get through to Barry and strengthen his resolve not to mess with time any more than he already has. A firm talking-to from Diggle isn't exactly the Airplane!-esque slap train that I was pitching for Barry as punishment for Flashpoint, but it would be much better than nothing.
Unfortunately, we may have to wait until the ginormous CW DC crossover to see Diggle discover that he once had a daughter named Sara. Felicity and Barry are currently the only ones who are in a position to break the news to Digg, and it's really news that should come from Barry. He made the mess; he should have to work to clean it up. Tune in to The CW on Wednesdays at 8 p.m. ET to see what's next for John Diggle post-Flashpoint on Arrow.