Should I also RP this idea?

ok, i've had this awesome idea that i plan on writing a fanfic of when i get time. the question is, should i also make an RP of it? I plan on typing the fanfic regardless, just i'm wondering if i should also make an RP of it to possibly get more ideas and to see a basic interest of it.

so here's the idea:

There is a world, a world covered in lush forests, gren fields, snowy mountains, and deep blue oceans. However, this world is conquered, controlled by an evil order. The group calls themselves the Promised. The Promised is composed of a secretive leader and five powerful generals, each with an entire military batallion under their command. The leader issues orders and commands the world, the generals carry out these orders. For the most part, while things are bleak, they are peaceful. The populas knows that obeying will prevent trouble, so they follow blindly to stay alive.
Another group is against this. This world is governed by various gods and long ago, it was prophecized that if the world itself loses hope in the face of danger; they would intervine. Suddenly people are born with magical powers that others traina lifetime for. These beings are born with a god inside them. Five humans with powers from the gods band together to defeat the Promised and restore hope to the world.

so, should i try an RP off this idea or just keep it as a fanfic?

 

it's original actually. i just said fanfic cause i'd be posting it in the misc section on Fanfiction.net