Diggle is kind of the group's true concience. Ollie and Felicity are there for personal reasons. Diggle has always been there out of a sense of right and wrong. Even when he is in a personal vendetta against Deadshot, we have the sense that he sees the need take this guy down for the greater good. As you say, Felicity and Ollie have no need to keep going once this arc winds up. Diggle sees there is a continuing need. He is giving Ollie this final training to be a hero and not just a vigilante.
The have been playing up Felicity's Freudian slips about Ollie, but it can't go anywhere. It makes her the nerd, even though she is hot, blonde, smart, fun, capable, etc. As long as she has an unrequitted nerd fantasy about Ollie, then she isn't involved with anyone else, and she can be the unrequitted nerd fantasy of all of us.
There is only one episode left, and Roy has very little to go in terms of tracking down his hero. He does know that Merlyn is involved, he does know about the "copycat" archer. He has a good bit of legwork to do. I do think he will be the one to pull Ollie's ass out this.
Moira is on a path to destruction now. Ollie knows, so she can never live this down. Walter knows that something was up, enough to know she wasn't what she presented. Enough to divorce her. Moira has no path to redemption that involves her survival. Possible exception is if she sacrifices herself, people see this, and she gets saved at the last minute. But this show has been too dark and gritty to give her a happy ending.
Laurel has always been somewhat attractive, but tonight seeing her at home in her shorts and socks jumping Ollie somehow made her sexier than anyone. I'm still wondering if she will become Black Canary.
Tommy absolutely has to hate Ollie now. I still have a hard time seeing him as credible physical threat. He doesn't have the killer instinct, or he wouldn't be so freaked that Ollie is a "serial killer." So far he has be the counterpoint to Ollie, he is what Ollie would have been if there was no island. For him to be a credible threat, he needs more than motive, he needs mad skills. What he has going for him, Ollie will never bring himself to take Tommy down.
Merlyn, something I just realized from the previous episode, Ollie's father said something about "We know one man can't do it" referring to the Glades. Now combine that with Merlyn's over-the-top skills, abilities, and equipement. What we end up with is a kind of Batman, one that was willing to go in with the League of Shadows. It looks to me like Merlyn would have gone the route of being a vigilante in the past. Have Ollie and Co. looked into this previously? Any going through old news stories, etc.?
I predict that Ollie will get out of this alive, but this has been a great setup and the show continues to impress me.
I'm sad that Lao Fe got killed.