[Destroyman]

Okay, I've had a few ideas in mind for a while:

Railroad Sentai Linerman: 5 train enthusiasts are given weapons & technology from another dimension to outfit their trains & stop evil interdimensional aliens from entering our world.
Featuring: Liner Red, Liner Blue, Liner Yellow, Liner Black & Liner White. And joining them later as their estranged ally is Master Conductor.
And together they combine their giant Liner Machines into LinerRobo.

OR

Constellation Sentai Zodiranger: 5 stargazers are blessed with the power of the Zodiac to battle evil aliens who consume stars, & their next target is, the sun.
Featuring: Aries Ranger, Taurus Ranger, Gemini Rangers 1 & 2, & Cancer Ranger. And joining them later is their estranged ally Ophiuchus Ranger.
And together they combine their giant Zodimechs into AstrOh.