I'm not familiar with the US legal system but this sounds to me like solving the wrong problem. Take the example of the game developer - why can't you create a

I'm not familiar with the US legal system but this sounds to me like solving the wrong problem. Take the example of the game developer - why can't you create a contract that says you pay her for 6 game ideas, including the IP to these games? It shouldn't matter if she comes up with those ideas during 9-5 or any other time. It shouldn't matter if she comes up with another 4 ideas of her own on the side, or even works part-time for someone else too. You're paying for an outcome, 6 games including all associated IP because that's what you're going to sell on to the public.