>>2315956>>SIC we're *NOT* missing:G3 Mild
Alternative Zero
Ryuga
G3 Mild is coming out in December as an exclusive. I never got the appeal of that version whatsoever. Alternative Zero and Ryuga were a set.
Furthermore, to poke at your list. RoboRider and BioRider don't need to happen. They were super forms and can be safely ignored. Frankly I'd say that all the engineering that could go into those two would be better of being used to create a more show-styled Black with his bitchin' ride Battle Hopper.
Movie-Exclusive Riders should not be created. Not so much in the case of ZO or Shin, but like Psyga, Caucacus, New Den-O and the like. There's maybe 4 new SICs in a year. None of the slots should be wasted on movie Riders (or for that matter, generic releases of Faiz "Riot Trooper")
Den-O is going to have at least 2 more releases; Liner + Zeronos Zero Form and Climax + Urataros(?). There still exists the possibility of more beyond that. Hence when Kiva probably gets milked next, they should only do Kiva -> Emperor, IXA (all forms) and Saga. Dark Kiva will be an exclusive, given the fact it's just a slight remold of Emperor form. All the forms relating to the arms monsters will be ignored, since even the show has basically done that.
As far as I can tell, SkullRider (homage) and Gaia (created in 2004) are not Ishinomori creations. All the SICs are characters made by Shotaro Ishinomori. I've never heard of Judo... is that a character from one of the Spirits books that hasn't been translated yet?