That would be amazing. A friend and I joked about how the series' big twist would be that Tassel is a metaphysical god-like being who turns out to be the real villain of the series.
On the real, though, I wonder if they'll introduce a new Calibur anytime soon. Or Espada. I find the fact that Kento is still in the opening highly suspect...

I'd rather see Tassel as a one-off rider for a movie or V-Cinema. Have him use a "Alice Of Wonderland" WRB.

Seeing as the smoke that took Sophia is the same that took Kurayami, we can expect Kento return as Calibur or maybe even a fusion of Cailbur and Espada and most likely become a brief enemy for Touma.

That would be quite fitting for him.

I wonder what the sword would look like, and I can already imagine 2 finishers that involve size changing. One where the sword becomes giant as he swings it, and one where he shrinks himself and gives the monster a death by a thousand cuts at superspeed.

Once thought of this easy upgrade for Kenzan, Slash, and Buster. Basically just a sort of black and grey suit that is shared for the three riders and then with only small differences to signify each rider. Like a different helmet and/or shoulder pads. Just to recognize them as enemies to Touma's goal and then return to their colorful forms after they reject the Southern Base.

Edit: and then there's this very interesting picture of Ren.

I wouldn't mind Kenzan getting at least a new normal Wonder Ride Book. Perhaps a Tsuchinoko-themed book to armor up his right arm and boost his speed.

That makes sense, but it also brings up a question.

Giving Kenzan a Mythical Creatures book would mean he would only need an Animal book to make a Wonder Combo, but he already has two Story books, so which one would he use in the combo? Ninja or Three Little Pigs? If he just uses his main book (Ninja) then what's Three Little Pigs for? Slash would be in the same situation.

One could say that their "main form" books are meant to go with their personal swords, and that a hypothetical Wonder Combo for their elements would use their "secondary" books, but that could mean Buster (and maybe Calibur) would need a second Mythical Creature book.

Or I could be overthinking this and taking it way out of proportion. Who knows, really?

Unless that serpent I spotted in the Gekido-themed Wonder Ride Book (there's one for each sword, with the sword name in the title) is meant to be a second head for the turtle, Buster may very well get a second God Beast Wonder Ride Book

Yes, Genbu is often depicted as a turtle whose tail is instead a serpent with a second head.

Huh. With this in mind, would a Wonder Ride Book based on a legendary serpent seem plausible for Buster to get during the series?