If you look at the way they draw the A, it's three marks. Ezra, Wren and Jason. It's a triple play with them working sometimes together and sometimes against each other. They've each had their own henchman. Jason had CeCe, Ezra had Mona and Wren had Melissa. Ezra has money. Jason has money. We don't know anything about Wren's upbringing except that his dad was nutso. He went to Oxford and was on the rowing team. They've sort of presented him as not coming from money but either he did or he's being funded by Ezra and/or Jason.
On the Labor Day weekend that Aria returned before school started, she met Ezra.
Spencer met Wren and I believe that was a set up involving Melissa. He put things in motion immediately to leave after he met Spencer. Let's face it, kissing Spencer in front of an open door and Melissa conveniently coming down the hall to see it? Melissa wasn't really that broken up. She still loved Ian.
Emily met Maya. We never saw her parents but I think they moved to Rosewood for work? If that's the case, somebody gave them a job worth moving for. The DiLaurentis' had businesses and contacts everywhere in Rosewood.
Hanna was best friends with Mona so she was already covered. Everything was put in place that weekend so each of them had a "handler". Mona was the A texting Ali but Jason put her up to it. It was probably him who trashed their porch on Halloween. After all, it was his house, too.
A couple of weeks ago, I did a post called "It's All About Ezra" going into some detail about him. Wren is the most mysterious and I think has the least power of the three. We really don't know his story at all.
Jason claimed that he was too drunk/drugged to know what was going on around him but we only have his word for that. There has never been any proof that he was telling the truth and he's really gotten a free pass in the investigation. He comes and goes with no explanation. If he hit Ali with the rock, Mrs. D would protect him. One other thing that I had thought of. When they were in Cape May and Ali had the pregnancy scare, CeCe asked her if Ali had told "him". Ali said she hadn't, that "he" would kill her. What if it wasn't the Beach Hottie that she was afraid of. What if it was Jason? In the flashbacks, we see that she was afraid of him and she wanted to get him disinherited which would make him powerless. If Jason had some kind of deal with Ezra and Wren, he wouldn't want Ali to come between them and make waves. If she got pregnant by one of them - my bet is Wren - he would really be mad.
Motivation for all this? Time will tell. The NAT club is a clue though. These guys liked young girls and were constantly taking pictures of them. Awake, sleeping .... changing clothes? naked? Could they have been selling pictures of them? Ali would set the stage for them to take the pictures. She even took some of Aria asleep, remember? She may have just thought it was their little hobby but it would have made her feel in control of her friends. She's a real nasty piece of work.
By showing Mona as A and someone taking her place, they've already set the stage for Uber A being several people. That would explain the difference in what they did to people. Ezra/Mona were in charge first and after Mona was exposed, Jason stepped up - he is Ali's brother and told one of the girls, Hanna?, that he was worse than Ali. He just hasn't been exposed yet. I believe he killed his mother because she started stalking Spencer. Remember her creeping up behind Spencer in her room?
I think Hanna is the anti-A. I think she's the hero who will step forward and actually bring A down. She's the most free thinking and independent of the four. With Mona gone, she has no real ties to Uber A - Ezra, Jason and Wren. With the relationship she's building with Holcomb, they will start working together and confiding in each other.
BTW, I think Jason slept with Ashley because of Hanna. He would have known Ashley was dating Pastor Ted and had an idea that Ted would propose. Everybody else in town apparently knew. Jason may have planned on blackmailing Hanna about keeping quiet so that Ted would never know. Hanna really wants her mom to marry Ted. That plan backfired since Ashley told Ted but ... yeah, that was a calculated move on his part. He knows Hanna is the wild card and Ezra had watched her talking to Holcomb several times.
All of these rabbit holes that Marlene gives us are exactly that, rabbit holes. That's why you can build a plausible case against any of the others. So she gives us dead people who might be alive and maybe some non-existent twins who are taking each other's place. All rabbit holes, my friends.