Tsubasa got some great development this episode. Love that she's gone past seeing herself as a weapon. The bit with her grandfather and mother left me stunned, geebus. Poor girl. ; ~ ;

Also HOLY CRAP AT VER RETURNING completely took me by surprise and that image is incredible

I really liked this episode. It was cool finally getting the plot, even if it was basically callable.

Also, just to reiterate, Chris's Ignite song and outfit are really excellent.

The series ends with a giant combining mech battle of all the gears vs. Carol's giant weapon thing

I agree.

I feel like they really went overboard with the whole senpai schtick for Chris in this episode. It was fine when it was sprinkled here and there but making it the entire point of her development this season is beating a dead horse. It wasn't very strong either in comparison to Tsubasa's stuff from the previous episode.

-Shirabe and Kirika being all "whoops sorry we helped the doctor because we were afraid of running out of LiNKER, our bad, won't happen again" when they should know better by now
-Sending Chris under the ocean to begin with
-There's no way SONG could've known Phara could hard counter swords but nonetheless between that and putting Chris in an environment she can't blow up both she and Tsubasa are being nerfed (and thus forced to Ignite) because hurr durr
-Phara and Carol gloating about things for no reason
--This literally only doesn't bite them in the ass because the situation just happened to align just right so they couldn't tell Chris not to Ignite/she was forced to because see above
-To reiterate, this literally only works because SONG just so happened to send Maria with Tsubasa instead of Chris
-Genjuro and the others can't even just send Elfnein out of the command room really

Also Chris's drama is even dumber, makes even less sense, and is even more forced than Shirabe/Kirika's thing. It's like they just decided that Chris had to be shoved into the same formula as the previous episodes but forgot until the last minute that she already had character arcs in the previous two seasons that covered her issues so they had no idea what to do now.

How the hell do you mess up "is afraid of being alone" so bad, [radio edit]ing Precure did a character arc like this better

Not even Ver could save this trash

Oh yeah, Shirabe and Kirika were royally stupid. Pretty sure Ver being on the loose takes priority over a lack of LiNKER. >_>

(I know she's been posing this way the whole time and the dolls' poses are all related to the dance style associated with them but I just wanted to link this gif)

- I thought Shirabe and Kirika doing that was tied into Ogawa telling them a few episodes ago that they only have a limited amount of LiNKER, and they don't know how to produce more. In that way, doesn't the Doctor have a point?
- Sending Chris to the bottom of the ocean was a bit of a miscalculation, probably, but Kirika and Shirabe were there with her. You could've swapped Maria-Chris, but honestly Maria's a better character anyway, so I'm glad she was the one on hand for Tsubasa's thing.
- Carol's spy was basically found and they knew there were being watched, so she had no reason to hide (and probably just wanted to make Elfie's life miserable). Phara had no reason to talk, but it's basically only to confirm what the viewers already know anyway.
- The static coincidence was a bit hurr-durr.
- I think sending Elfein out of the command room would've missed Genjuro's point. He wanted to prioritize Elfie's feelings of belonging and being one of the team over the information leak, and show Carol that he wasn't bothered by her apparent advantage.
It would've been weird to say all that about accepting her and then go "now get out of the room." It would've made more sense, though, for Elfie to volunteer to close her eyes and plug her ears at that point, or something similar. Maybe.

That's because Chris is a shitty character

nah j/k, it is a little rehashed, but this is the season of rehashed plot arcs (Tsubasa aside). And I don't think Chris's was rehashed:
s1: Is it okay for me to have friends?
s2: Can I make up for what I did before?
s3: Can I protect my friends, and can they rely on me?
The answer to S2 is a kind of obvious "yes," but I think here it was more that a) Chris got carried away with what it means to protect (similar to what Kirika and Shirabe did), and then when she thought she had actually failed, and Shirabe and Kirika were killed, then she fell into despair.

I'm not saying it's objectively good, just that it's in-line with what Symphogear logic is in general. It certainly wasn't as bad as you're making it out to be