What if Ezra has been working for Byron all this time? We know Ezra attended college while Byron was teaching there; since they are in the same field of studies, it seems strange that they've never crossed paths.
Maybe Byron was having an affair with Ali, maybe then she wanted more and started creating problems, and when she got to know about Meredith she became too dangerous for Byron. Maybe he asked Ezra to get close to her to be a distraction or frighten her a little bit and then things got messy.
I don't know, it kind of feels strange that Ezra would only fall for underage girls. Once might be love, twice is a pattern, unless it is planned.
If that is true I think the Ezra+Aria thing was not part of the plan, and maybe the reason why Byron was initially so mad about it but then let it go rather easily is because his position was too dirty to start a fight with Ezra. Maybe Ezra felt the need to stand up to his "boss" for some reason we don't know.
As I already explained in this post, I think IF Ezra is gonna be big A he's gonna be that alongside Aria. But I could see him being somebody's "worker" and not the mastermind.
Byron is a dirty cheater and a little creepy, and Ezra's excuse is pathetic. Timing and circumstances seem to indicate that they should have met before it all started, but they played it like they had no clue about each other. They might not be big A and his worker, but I think something is going on between them.