[XW1n5t0nX]

You could actually tie in cars and military themes together in a clever way which could actually lead to a sister series. Basically the military force has two teams of special elite soldiers (the rangers), one that specializes in air/space/flying combat and missions, and one that is stationed on the ground. Have the ground team's mecha be based around military vehicles that go with that theme such as tanks, trucks, etc.

That way you get both a car and military themed sentai. Plus as I said, it can lead straight into a sister/sequel series that can be about the air team.