Got the idea from Super Sentai and Kamen Rider.
(Rebellion Squadron JohtoRanger is the English translation for the name)
Giovanni is back to finally revive Team Rocket one year after HeartGold and SoulSilver. However, he has a new tactic: Instead of using humans and their Pokemon, he is having human/Pokemon/machine hybrids created in his base to conquer Kanto and Johto. Giovanni has also seemed to have obtained more of Mew's DNA in order to create these atrocities.

Arceus sees this happening from the heavens, and decides to call upon Mewtwo, Giovanni's sworn enemy as well as his first "Creation". This also is personal.

Mewtwo calls upon three teenagers to harness some power from Raikou, Entei, and Suicune.

Later, Lugia, Ho-Oh, and Celebi will give some power to three more teens.

The teenage humans will use Morphers, powersuits, weapons, and "Zords" that become a "MegaZord" when combined.

Also, they will have "Weapon Zords" like in PRNS , which are based off non-legendary Pokemon.
Starters:
JohtoRed/Entei Ranger from Azalea Town (Gabe Mendoza) gets Bulbasaur
JohtoBlue/Suicune Ranger from Goldenrod City (Courtney Liu) gets Charmander
JohtoYellow/Raikou Ranger from Cianwood City (Taj Singh) gets Squirtle
JohtoGold/Ho-Oh Ranger from Mahogany Town (Peggy Owen) gets Chikorita
JohtoSilver/Lugia Ranger from Vermillion City (Eric Damon) gets Totodile
JohtoGreen/Celebi Ranger from Fuchsia City (Nadia Romanov) gets Cyndaquil

More to come.