Oh right, I dunno why I didn't think of that, sorry!

No word on who the cast are yet? I recall last year the Build cast were announced around the time of Ex-Aid's movie, but I haven't seen anything as to who the cast in this series are yet.

The official series press conference is currently scheduled for August 7th; we should learn the cast & probably a bit more about the story then too.

Looking back over the toy scans, I don't think I noticed the first time that the Decade form isn't Zi-O or Gates/Geiz. (It sure sounds like "gates" in the audio.) To the upper-right of the upgrade, there's an image indicating what the face looks like when Zi-O is using the Decade upgrade. It looks like the Decade Ride Watch has a slot that can accept other Ride Watches, and demos Zi-O/Decade/Build. I... must not be observant.

It's officially 'Geiz' - its pronounced identically to 'Gates'.

98% chance you're right, but I'm waiting to see whether the belt truncates or alters longer names.

Longer names are scrolled across the screen, and he was called "Kamen Rider Geiz" in promotional material for the new Switch game.

For both Geiz and Zi-O, the name is briefly a static display. I wonder if that's why they chose "Geiz" as that Rider's romanization. I suppose I'll only get that question answered if the show introduces a tertiary Rider with a name that'd be romanized past four characters.

Come on, man, you're reaching now.
It was done for the same reason as Cross-Z - to look cool.

I don't think it's really a stretch to suggest that the name is four characters to fit in the digital display.