I think as others have said, that idea itself may not be quite right and you are looking to us to brainstorm. However, I do know someone who does exactly this, for free. He makes his money by facilitating the ability of others to think outside their proverbial boxes, using what at the core, is basically workshop facilitation. That's an easier sell than 'professional ear' as the market is kind of there already. You don't have to know much about the business to facilitate a workshop or coach per se, as you need to concentrate on the facilitation. Many people like me can't think and facilitate at the same time. :-D Especially if you're too close to the problem. So effectively you get called in ad hoc to facilitate workshops to allow all the firepower in the room to concentrate on the problem at hand. It doesn't mean you can't structure a session where you give advice at certain points or when asked. However, that risks exposure. You can always help by researching after the fact, where the team has found key questions they want answering. Write them on a post it and take them with you.

If you become a millionaire off these ideas. I'll take 10% ;)