I'm guessing for the henshin of Another Zi-O, the new guy will just simply click the Ridewatch, it'll summon the belt for it and slide it. Simple henshin like Gold Drive.

Possible. But I think its more likely that it'll just happen the same way the others all do. He's still just Another Zi-O, after all, not Kamen Rider Another Zi-O.

He has the same belt as the future Riders, complete with his Watch on it though, rather than the Watch just disappearing after transformation like with the previous Another Riders, so a different transformation wouldn't be that surprising.

I didn't say it would be surprising - just that I find it more likely that he won't get one.
Also it isn't the same belt - Another Zi-O's has a screen, unlike the Future Riders.

The future rider belt has an empty space where the screen is supposed to be, and Another Zi-O's screen is in the slot. Perhaps a future Premium Bandai release?

Can't exactly tell but what I can see on the Another Zi-O screenshots it's just a clipped on 2019 on there, wouldn't surprise me if the Another Zi-O watch came with panels you can click on the Future Rider's Belt with years on them

That slot is probably for Kamen Rider Ginga.

Heisei Generations Forever is going to premiere in Malaysia, date unknown, but sources say it's the end of March.

https://www.facebook.com/TGVCinemas/...type=3&theater

Seems like another Zi-O will be able to change into the other another riders

We've known this for a week now, yeah.