Head writers are given the suits, toys, and basic story outline/what direction Toei, Bandai, and TV Asahi want the show to go in. They then write a story around that. Sometimes audience reaction can change certain events but most of the time it plays out as the writer intends unless the show is doing really bad in the ratings or toy sales, in that case Toei will step in and make executive changes in order to boost the shows popularity (or get the budget back in line). The writer doesn't get to throw in their own opinions like deciding what characters get power ups, how many riders the show will have, or what the show will be about. Bandai designs the suits, toys, gimmick items, forms, etc. They then sell the toys of those suits & forms. Toei films the show, edits the show, and hires the cast/crew. TV Asahi airs the show and finances the show. Avex handles the music. So whenever a new form/rider gets announced, it's Bandai who decides what the rider/form will look like, all Toei does is film what they're given by Bandai. Toei & Bandai together own the show and they're in a partnership with TV Asahi who hires Avex.