Good implementation is much more than an idea and a developer to build out that idea.
That is my point, what if you get in this situation and it looks like you are hired as a "contractor" but the client is only bringing the idea to the table and the rest is up to you?
That would be quite ballsy on the part of the client. There's too many variables that aren't mentioned in your hypothetical situation to make a case. If a client came out with an idea and proposed hiring me for it and seemed too clueless to give me much else for input then I would probably decline the project. I just wouldn't trust this person to not flake out on me at some point and cause a bunch of headaches for me. I'm busy enough as a contractor that I wouldn't need to take on something like this and an important part of contract development is knowing when to say no.
