This episode is kinda dragged down by too much conveniences:

1. Misora just walks into the wall and push the Seito's trio far as soon as the Touto's and Hokuto's riders are under and she happens to have martian powers.
2. Nanba happens to grow child soldiers
3. Looks like no one is intercepting Sento's communications with Souichi.
4. Misora, again, walks into war zone. Without Sawa behind her.
5. Rogue, again, doesn't finish the riders, just jumps away with the Pandora's Box.

This actually one of biggest villain weakness in Kamen Rider because many villain in Kamen Rider always escaped despite they has huge chance to kill the heroes. Also, this can be considered as plot armor :D

If I am Gentoku, I will kill all Riders and then, I will steal Pandora Box...

This time it's probably due to Gentoku not wanting to actually fight Max Hazard when Kazumi inevitably gets beat and just taking what he can now.

The first time he kicked their asses as Rouge though, yeah I dunno.

She's literally always had Martian powers. Martian powers is all she's done all series. What did you think the bottle purification and healing was? There is nothing contrived or out of the blue about this development.

What war zone? The warehouse they were keeping the box in could be literally anywhere, and it was just a warehouse, not an active warzone. She knew where it was. And what does Sawa have to do with it?

It's almost as if that's his primary goal and they've done a pretty solid job of keeping it away from him so far, and also almost as if the girl who just walked into this situation literally just chucked him across the wall that morning. But you're right, prioritizing his main objective just feels contrived.

1. I was emphasizing on more about Misora walks into warzone, barefoot, out of nowhere. Didn't even have comments from Sawa regarding that. "Oh, Misora was blinking out in front of me, and then she was on that warzone". Everyone knows she has powers from the pandora box, but literal martian powers are still in question. Now the fact that she has martian powers is indisputable.

2. Wherever the riders fight, it's a warzone, even more so compared to zone where the soldiers battling each other. Sawa usually is behind running after her because she usually is the one driving any vehicles they are using to get to the warzone.

3. He's more about effectiveness and removing every obstacles in front of him. The riders are obstacles, and the girl was just chucking him out through the wall, not blasting him with damaging firepower. He could just easily kill the riders with overpowering explosions, and hopefully the girl too, and then escape. It's not like killing the riders, out of armors, is hard for him to do.

If this was any other show, I wouldn't make mention of it. But Build had a lot of bike action in the first quarter of the show, including with Ryuga. I'm wondering if the lack of bike usage now is because of funds going to film the Amazons movie. Perhaps once that is done we'll see the bike again. Or if not, then the Build movie may at least have one bike scene.

This still doesn't explain why Grease and Rogue lack bikes, not even copies of the BuildPhone or "civvie" bikes.

I doubt the budget for the Amazons movie is why the bike action has lowered.

My reasoning here is that budget meetings, contracts etc. Are usually decided a year or two before most of the shows start full production, now I have no idea how they have set up the budget for Build itself, it could be a total amount for the entire season, or every 3 months etc, like most studios they likely have a ton of Rider season ideas and potential budgets planned if they decide to go for this or that, any creative branch will have a TOOOOON of stuff they might never end up doing but setting up potential budgets for them is very likely, some of this stuff can take years of planning, most of which never happen, but they still have to get budgets and contracts ready just in case.

We also have to take in mind the permits they have to deal with in order to even do the bike scenes, they might not have the option to do certain things until certain dates due to legal reasons etc.

Their studio personal sets they can use for the stunt works are also likely not available for the team doing Build all the time either, there are other shows they are working on at the same time at the same locations and so on.

Now budgets are not always locked either, most studios tend to either agree on lowering a budget or increase it depending on various factors, so it gets more complicated.

It is clear that various things can strain a budget, shit happens etc. With shows like these that are running the entire year, we are going to get weeks where they literally could not afford to do what they originally planned so you end up with VERY cheap looking episodes now and then, suddenly they ended up having to spend more money then planned and due to that the next weeks episode has to cut and gut itself and you end up with shoestring budget weeks XD