Ghost Rider hasn’t anything to do with ghosts in the definition of the word though.

If I think Ghost-theme, I can actually see something like W, Sixth Sense and Haunt thrown in a blender. Protagonist can see the souls of the dead, monsters eat their souls before they can transcend into the afterlife. Soul of the dead brother/sister of the protagonist is bound to him and when they "fuse" they create Kamen Rider Ghost who fights the monsters and frees their souls. Something like that.

Or something entirely different because we no nothing about it yet. But the name sounds promising enough.

Or something like Yu Yu Hakusho would be cool too where our main rider becomes a ghost detective after death investigating supernatural activity within the Human World from evil spirits. However Drive was already a detective, so I can't see that happening.

Ghost can go alot of directions. Will it just be a transparent dead guy like Sixth Sense?
Or a monsterous Ghost like in horror flicks?

Vampire x Ghost cross over starring Kiva writes itself right?

Renewal Kiva confirmed

It's a Kamen Rider who can see the ghosts of all the deceased past Riders and briefly transform into them.
Decade: Dead People Ver.

If it is a Ghost theme, what could the rider collectable gimmick be....

Tombstones could be a interesting Idea...

Coffins... nah too simple.. Ghosts... Ghosts...

If it gives us Zanki and Yoko as recurring characters I'd be down for that. Maybe Kusaka could be the main villain.

Spooky Scary Skeletons.

But to be honest, this is also a good idea, even if it one I swear I've seen on a poorly-drawn rider on DeviantART. Chances are the enemies are going to be vengeful ghosts. I do believe Japan ain't to shy with those types.

As for gimmick-ability, I don't know...Ghost isn't immediately indicative of any collectables, so it's likely something none to obvious, probably steeped in Japanese ghost tales.

Also: Kiva vs Ghost = Yus Plees.

Hmm. You got a point about Gimmick-wise for Kamen Rider Ghost.

You know there's always be a gimmick in both Super Sentai and Kamen Rider because Gimmick are popular for little kid or maybe teenagers

I know Riku Sanjo is very unlikely to write Kamen Rider Ghost since he is currently writing Kamen Rider Drive.

I hope Toshiki Inoue won't write Kamen Rider Ghost after his mediocre Kamen Rider Kiva which is a horror-themed.

I will wait until October

I always thought Kiva would have been better if they'd not gone with the whole 1986/2009 plot thing.

Edit; Had a Thought what if the gimmick is charms and The rider suit incorporates Shinto priest/exorcist aspects