First, I should point out that "sentai" roughly means "taskforce". Individual members are usually referred to as senshi (warriors).
Needs a fear effect on Background Explosion/greater fear from posing as a team than solo.
Also, some way to combine attacks. Maybe if you ready an action to attack at the same time as a fellow sentai, the damage from your attacks is combined? Or if everyone does it while adjacent to each other, the attack becomes a line.
Maybe gain a single ability based on colour. Red gets inspiration abilities which he can redirect to himself when he sees his teammates defeated (think Inverse Ninja Law). Other options include faster maneuver recovery, Powerful Build, virtual ranks in all Knowledge skills, and Cha to AC.
The enhancement bonus for the weapon/armor is pretty low, and it doesn't say if you can enchant them normally. I'd also suggest some ability which lets you Quick Draw the weapon and convert it between different forms (the weapon also gains the aptitude
property). Because guns that turn into swords/vice versa are a staple.