You will definitely need to describe this system and how you think it should be implemented. There have been issues in the past where people just asked for an FFX battle system and got what they asked for...but not what they wanted, as both they and the coder didn't agree on what that meant.
Also anything is possible, if you can code. But it will not be easy. If you've never made a game before forget trying to do this now, instead make something that uses the system that is already in the engine. Then once you get experience with that, the try something more advanced.
And if this is for the IGMC, forget it. Unless someone has a plug-in already made, battle plug-ins take months to write, so there's no way someone could code this before the IGMC deadline for you.