[806mtson]

Though, let's say that there was a meeting of the main Riders from each series. They introduce the new Rider, and their first reactions are "wait, there are two of them."
Ghost: I heard your series is ending.
Saber: Yeah, I wonder what the new Rider is like.
*In comes Revi and Vice*
Drive: Uhh, this is only a meeting of Primary Riders. You brought in a Secondary Rider.
Revi: We ARE the primary Rider.
Vice: Yeah, we are together.
Fourze: So, what is the situation like?
Revi: I am Revi.
Vice: I am Vice.
Revi: And together we are
Revi and Vice: Kamen Rider Revice.
The Riders: Huh?
Revi: Our situation is sort of reverse of Double's Situation. Instead of being Two in One, it's One in Two.
Ex-Aid: Sort of like my Mighty Brothers XX.
Revi: A bit like that.
Vice: But I'm a Demon that resides inside Ikki's Body.
Ghost: Wait, Demon?
Den-O: So, sort of similar to me.
Revi: Yeah. So it's sort of a cross between Den-O's Imagin and a reverse of Double.
OOO: Okay, so what is your collectable Transformation Device?
Revi: They are called "Vistamps".
OOO: Oh, named after Vice?
Vice: Likely that's true in the production, but in fiction, it's a total coincidence.
Fourze: What are you talking about?
Revi: Yeah, he talks to things that don't exist.
Wizard: What are these "Vistamps" based upon?
Revi: They are a cross between Extinct Creatures, which you can see as our main form is based upon a T-Rex
Vice: And you guys.
All Riders: WHAT?
Revi: Yeah, we are an anniversary season, but unlike Decade or Zi-O, the forms aren't directly based upon you guys, but they are based upon them.
Kuuga: So, what Vistamps have been confirmed and who are they based upon?
Faiz: I'd prefer if you told us which of us have a Vistamp based upon them before.
Revi: Okay, so we have the Vistamps based upon Kuuga, Faiz, Den-O, Decade, Double, Fourze, Gaim, Ex-Aid, and Zi-O,
Vice: with one that hasn't really appeared in the show yet based upon 1.
Kabuto: Okay, so what are they based upon?
Revi: So, Double got the Eagle Vistamp, Den-O got the Mammoth Vistamp, Decade got the Megalodon, Faiz got the Ptera Vistamp, Kuuga got the Lion Vistamp, Ex-Aid got the Jackal Vistamp, Fourze got the Kong Vistamp, Gaim got the Kamakiri Vistamp, Zi-O got the Brachio Vistamp, and 1 got the Batta Vistamp.
Zero-One: So, I get the 1 Batta Vistamp, but why the others?
Revi: Mostly aesthetic Reasons.
Vice: We also have this interesting ability to make "Remix" Forms, which combine us into the animal this form are based upon.
Saber: Why don't we go to the Form Showoff Room?
Revice: Where is that?
Kiva: It's where we show off our forms? It's large enough to show off mech Forms, so you could show off your Remix Forms.
Revi: Yeah, let's go.

This is sort of a mini-fanfiction piece. Not sure if this would be their reactions, but I don't know.