Red Ranger
Member
Considering from the preview for this weeks episode that Ouja is the original voice, I'd assume that he is summoned by Narutaki.
Occham's Razor. Most likely he can summon any rider, regardless of their status in each world, AU or not. They're only drones anyway.
Eh... Narutaki's Riders clearly had personality, the Hoppers even disobeyed him, going after Kuuga rather than Decade and Kick Hopper was clearly angry when Kuuga attacked Punch Hopper. Kaixa even talked about stealing Decade's belt.
Anyway, Diend has many cards, but not every single one, otherwise he wouldn't have needed a real Den-O to use a Final formride Denliner.
diend's riders do too, remember last week in episode 18? when he summoned den-o and FFR'ed him into momo? momo got angry at diend cos he interupted his "ore sanjou". i might be wrong but thats wat i think