You are going to need a game design document, thats for sure.
It needs to include concept art, story, mechanics, rules, time scales and targets etc.
As a lone developer it might be possible to keep all this info in your head, but for a team to develop your game they are going to need precise information on how to complete a given task. Eg, if you want a tank to move at 15mph, it needs to be stated by you. If its not, it will be open to speculation and you could end up with a tank moving too fast or too slow, simply because it was not specified.
Sure, you could have a team do brainstorming this design document, but it would no longer be #your# dream.
Im sure everyone here wishes you luck and fortune, but for the sake of your success and sanity - preparation is imperative. As they say, failing to prepare is preparing to fail.