I agree that there is a group of Others that are Richard's people, not Ben's. Certainly Richard commanded the Hostiles, and Ben was DHARMA. After he was healed at the Temple, he did help Richard (and Jacob?) kill the DHARMA folks. He had already killed his own father. He seemed to be a nice little boy, so I'd say he did change! But supposedly he served Jacob, not Smokey.

I don't think we know whether the Hostiles came and occupied the DHARMA barracks after DHARMA was wiped out. Some may have. At least some stayed with Richard out in the wilds, at the statue? (Didn't Ben say that Richard was easy to find because he'd always been at the statue?) Then clearly Ben AND Richard recruited people. Richard and Ethan recruited Juliet. Ethan took orders from Ben. He lived in the houses, not with Richard. But he and Richard worked together in some situations.

btw, I looked up the scene where the Temple guard appeared before. For those like me who didn't remember him exactly, Aldo was the Other sitting in front of the building where Carl was being brainwashed, reading "A Brief History of Time." Alex, Sawyer, and Kate tricked him, and Kate knocked him out with a rifle butt as he said, then later Danny found him and yelled at him. No wonder he's sore at Kate.

(Season 3.7, "Not in Portland."
The writers could have used anybody as a Temple guard. They didn't have to bring back Aldo and have him specifically remind Kate about the events on Polar Bear cage island. They're making it clear to us that the temple people have a crossover with Ben's people.

Alex tricked Aldo by telling him that her Dad had sent her. So we know that Aldo answered to Ben. Now he answers to Dogen. We haven't seen Richard interact with the Temple people yet. He took Ben to the Temple in 1977, but the personnel would have been different.

Writers having fun echoing: as they stared at Aldo wondering how to get by him, Alex said "I have an idea," and Sawyer says sarcastically, "of course you do." In What Kate Does, Justin tells Aldo (about the decoy trail) "I think she's right" and Aldo says "of course she is" with the same intonation.

As far as the change in people goes, there seem to be different processes.

Ben didn't die of the gunshot wound, as far as we know. Sayid died, and the spring wasn't clear.
Eko's brother died. Christian died. Smokey seems to have possessed their bodies. Smokey created an apparition of Walt, but he was not only not dead, he was elsewhere on the island, so that wasn't Walt's body. Nor was it Kate's horse that appeared to her.

Locke died, off island, where it's not clear that Smokey can travel. Presumably he was "inhabited" after the plane crashed, similar to what happened to Christian.

We don't know what happened to Claire after she disappeared. She doesn't seem anything like Locke. She is wild, like Danielle. But Danielle hadn't lost herself. She remembered her daughter.

With Sayid there's no sign that he's "fake" Sayid as we saw with fake Locke. He has the same personality, whereas Locke had a new confidence and attitude. Sayid is infected and is going to change gradually. This is what Desmond was afraid of and why he took the vaccine, I would imagine. Or why he thought he was taking it.

In Fire + Water, Charlie had visions that Aaron was in danger and needed to be baptized. Also, Claire was persuaded to give Aaron the vaccine. And of course Claire was being treated (but they didn't have enough medicine for both her and the baby? What was that about?) So it seems that children are vulnerable to this infection, and probably that relates to the thing that makes pregnant women die?

I'm pretty confused about it all. I think we will understand what this is about very soon, but I don't think it's clear yet.