[kamen rider Q]

So, let's take a look at our So-Do "To Make" Backlog:
From Zero-One we have:
Orthoros Vulcan
Horobi Ark Scorpion
Ark-Zero-One (although unlikely since they didn't even bother with the unique design of Woz armour even with their promise of completeness.
Possibly more Magia or Raiders as demonstrated by Jackal Raider
And Saber:
Buster
His Jakkun arm
Kenzan
Kobuta 3 Kyoudai armour W/ Kenzan's arm
Slash
Peter Fantasista armour (Saber and blades head)
Tenkuu no Pegasus armour (Blades head)
Needle Hedgehog armour (Saber and Espada head)
Storm Eagle armour (Saber head)
King of Arthur armour (and robo at some point)
I really hope that we end up getting alternate heads for all of the in-show users and combos, at least those that actually appeared in series, along with heads for the likes of Buta3 and Pegasus which have only appeared in triple combos.