[henshinzero]

1) Birds, since OOO, I thought of Jetman. Mix that with a spec-ops motif.

- Metal Gear Solid
- KR Kabuto
- Birds/Owls - Guardians of Ga'hoole
- Bats/Flying Animals - Silverwing
- Silverhawks

The kaijin can be like the Mavericks from Megaman X & Zero.

Final Form: Phoenix

2) Treasure Hunting. Since Boukenger & Gokaiger, perhaps a treasure hunter like Indiana Jones & Nathan Drake, he'll be the main hero. The secondary rider would be a rogue pirate.

The kaijin would be pirates based on aquatic animals, with the sharks as the main villains.