Here are my thoughts - just my opinion of course.
If Finn doesn't know where "the Basement" is, then Effy wouldn't have been able to trace the hacking to there, because Finn was behind the hacking. We could still go that way, but we'd have to figure out a different way to explain how Effy knows to get there. Like...Effy and Olivia find Finn's base, and there's some sort of bug or beacon whose signal leads them to the basement? Like MysTech had been watching him all along? OR in the time between leaving Olivia's apartment and meeting at the Roosevelt, when Effy didn't post anything, she COULD have already been to Finn's lair and found the location of the Basement.
So, just to make sure I understand, we have Brenda, Jack and Rich trusting Finn, thinking he's ex-MysTech and going to help them take it and Shade down. Shade is still the enemy from their perspective. In reality, Finn is using the kids to get to Effy and this MysTech stronghold. Right? What is his purpose in looking for it? Just that that is where he will deliver the kids?
I'm not sure Farrah will go along with Shade being "good". As I know she wants to use her later and she is supposed to be a total killer, not like Dominique. Maybe I'm not understanding this part though. What would work well would be to have Dominique and Shade actually have teamed up, so that at that point Shade offers them to join her and Dominique in the Hellfire club. Because THEN Brenda, Jack and Rich could have some realization that Effy and Olivia were indeed RIGHT, and that would allow the whole team to be reunited. That would have more bite than it just being a divide over Finn essentially.
I see the end one of two ways. One, Finn and Shade capture/subdue Effy and Olivia, backed by Brenda, Jack, and Rich. Finn betrays Shade, and he does something to her that incapacitates her. His plan is revealed. Now Brenda, Jack, and Rich know they've been tricked, and they have their "aha" moment and free Effy and Olivia. The team kills Finn, and destroys the facility. Shade is trapped inside and believed to be dead. The kids escape, now a team, and everything is bright and shiny and new
Second, Shade kills Finn when she is betrayed. She could then make her offer to Brenda and Rich to join her (and I still think making her in league with Dominique here is a good idea) - the price being taking out the other three. There could be some sort of moral dilemma yadda yadda, but they say no, and the kids become a team again and unite against Shade. They kill her, destroy the facility, and escape blah blah blah.
lol