[FairyKing]

This might be too dark for children, but what about Sentai mixed with military scifi elements like space marines? I give you Jūkaki Sentai Senshiger! (Heavy Weapon Sentai Warrior-ger)

In the distant future, the Star Alliance, a free and just civilization where humans and various aliens live in harmony, is locked in war with the Dargrim Empire, a conquering army where the strong oppress the weak and any evil is permitted in pursuit of more power. Alliance forces are quickly losing ground against the Monster Troopers created by the Empire's horrifying experiments, until a group of their own scientists develop revolutionary new technology based on heroes from Earth's past. These are the weapons, armor and vehicles of the Senshiger system.

What sets Senshigers apart from past Sentai teams is that the rangers aren't unique, there are several of each color, with rangers of the same color being distinguished by different designs of helmets. The story would probably mostly follow one "main" team, but they would often work alongside other teams of Senshigers, and some episodes could focus entirely on other teams.

"Command Red!
Skirmish Blue!
Heavy Yellow!
Medic Pink!
Recon Green!
Jūkaki Sentai Senshiger, move out!"

Other colors who aren't present in the main team but would show up in other teams:
Pilot Cyan
Fortress Orange
Covert Violet
Hazard Lime

One-of-a-kind Senshigers:
High Commander Crimson, the main Red after being promoted to lead the entire Senshiger army.
Admiral Navy, captain of the Senshi Battlestar, the largest and most powerful Senshi Machine that serves as the Senshiger's central base.
Proto Black, the original Senshiger suit, now used as a test bed for new technology, extremely powerful but dangerous to use outside controlled lab conditions.
Traitor White, a rogue Senshiger who joined Dargrim, losing his color in the process (has a skull motif)