[Sunred]

So here's what I think could be in store for Zenkaiger's tsuika senshi. The 6th member to join will be green and is a ninja-themed kikainoid who uses the Hurricanger gear. Now let's remember, Hurricanger was the 10th anniversary of the official start of the tsuika senshi and this was evident when it was revealed Shurikenger had the same palette as Zyuranger's Dragon Ranger Burai complete with extra gold armor on top of the green suit. And yes while technically X1 Mask came first he is a bangai hero/senshi at this point because Dragon Ranger is officially the start of the tsuika senshi.
So, because Zyuran has the Zyuranger gear, this new ranger is a ninja-themed Kikainoid who utilizes the Hurricanger gear because either:
A. At some point during the show appears and steals Zyuran's Zyuranger gear only for our heroes to take it back and teach the ninja a lesson, but later finds the Hurricanger gear along the way and becomes a Senpuujin-themed green Zenkaiger(or maybe a Tenkujin-themed to match the tsuika senshi concept) and goes solo at first while being salty towards them, especially Zyuran
B. This tsuika is the Ultraman Z of the show and has nothing but the utmost admiration and respect for Zyuran begging for a shot at aprenticeship or just tag along and admire the old man while Zyuran finds all this annoying

Another speculation I have, and ditching the ninja theme, what if said kikainoid is a sibling, rival, or nemesis to Zyuran and is brainwashed by the Tojitendo. The kikainoid would then be using the Abaranger gear and let's not forget, the bakuryus were green when brainwashed and prior to bonding with their ranger partners.