Some character summaries as well as info for Zeztz's first quarter power-up provided by Color809 as well as another Tieba user (contains spoilers):

Baku Yorozu
An optimistic young man cursed with bad luck. Lives with his younger sister Minami, who is the sole breadwinner of the family, as Baku's poor luck has prevented him from finding a job. One day while job searching, Baku falls into a coma after saving a kid from an oncoming car (an event caused by creatures called Nightmares). While comatose, Baku finds himself inside the dream world dressed as an agent (his personal interest are things related to spies). After encountering 0, a transformable motorcycle who is also the leader of the secret organization "Code", Baku is recruited into the organization as Agent No. 7 and transforms into Kamen Rider Zeztz. After working together with 0 to defeat the Nightmare responsible for his coma, Baku miraculously wakes up as the Zeztz Driver also materializes into the real world. Baku's awakening from his coma has also caught the attention of police investigators Tetsuya and Nasuka.

Nemu
A famous actress/idol who, like Baku, has the ability to enter the dream world. Can freely switches her clothing while in the dream world, where she usually meets and interacts with Baku.

Nox
Baku's rival. Responsible for guiding the Nightmares into the real world. Will eventually transform into Kamen Rider Yezz, the secondary Rider of the show. Apparently is a former cop.

Tetsuya
A hot blooded police investigator very dedicated to his job.

Nasuka
An elite police investigator who is very serious.

Minami Yorozu
Baku's reliable younger sister.

Zeztz's 1st Quarter power-up will be called Inazuma Plasma, which is gold and gunmetal silver in color.

The James Bond nods are neat, but now Baku just sounds like Ace mixed with Keiwa. Nemu is sounding a lot like Neon 2.0 too. Nox's whole rogue ex-cop angle might be interesting though, while the two actual cops sound like they will mostly be comic relief just going off their perfect comedy duo personalities. I'll be really shocked if the Yuuya Takahashi rumors turn out to be false at this point, pretty much everything about it screams his style.

Yup. Baku is Ace + Keiwa in one alright. Unlucky cool. Tho the mix might hopefully be unique and not bland. Fingers crossed.

Wait, super bad luck, has a reliable sister, has four base forms that utilize a weapon that can by default transform into four different modes... one of which include an axe...

Guys, that ain't Ace...

That's Ryotaro Nogami.

Exactly!
Although, if in their family there is a more reliable and socially successful younger sister, then this gives Wataru a little.

Well, I doubt he'll get much screentime doing bike things, but it's cool how the bike will be an important character.

Glad I wasn't the only one who thought of Ryoutarou before Keiwa. Ryoutarou is actually super unlucky, whereas Keiwa's problem is that he screams World Peace at job interviews. The main difference with Baku is that he has a reliable younger sister.

I actually really like this preview. Byaku looks like a very interesting character. The active participation of the police in the plot is also pleasing. Bike as the leader of a spy organization is something new and incredibly cool, I can't wait to see their dynamics. The secondary rider/former villain is also very interesting. Although, I'm not sure if Yezz will be secondary or if his participation on the villain's side will be very brief, in the style of Vroom from Zenkaiger. The younger sister also doesn't appear in the plot as often as the older one.
I don't know about Yui Takahashi (did his riders even have sisters? Ace's relationship with Tsumuri doesn't count), but this description gives me more of a late 2000s/early 2010s shows vibe.

True, Shizuka is a reliable mother despite her young age.

Not sure what the name Yezz is supposed to mean though. Even just using the given name as Kamen Rider Nox sounds better to me.

Takahashi's Primary Riders mostly have complicated relationships when you think about it. The M personality was born from Parado's asexual reproduction. Aruto has all the robot uncles and aunts created by Korenosuke. Even if you don't count Ace's desire to become DGP family, Tsumuri and Neon both came from Mitsume.

I just have associations with Yes, with a long z to match the style of the particular show. Hopefully it makes sense in the context of the character.

In that case, if he is the scriptwriter, it is worth taking a closer look at Minami. She could very well be a dream that has come to reality, or an undercover agent. Or both.

For sure, I can see either or both of those possibilities happening. Takahashi wouldn't hesitate to use the memory manipulation trope to make everything mysterious.