Here we go again.
People ask me to work on dumb ideas for free. I don’t. The decision is simple and the process is short.
People offer to pay me to work on dumb ideas and most of the time I dont. Schedule permitting, I can be bought.
People ask me to work on good ideas and pay me, this is the norm of the work I do.
People ask me to take good ideas and make them better and more successful, they pay for the project and a negotiated royalty. This is the ideal.
And some people ask me to invest my time, money, intellect and energy in various projects, of which some involve design. I make that decision based on all the factors.
The world (and recently embodied by Kickstarter) is full of people floating ideas and taking risks in new ventures. To maintain that the only person in the chain that should be 100% risk free is the designer, is misplaced.
I can understand the passionate personal decision to insist on payment up front and no risk. I cannot accept attempts to force that same view on everyone else.
To the original poster, this offer is not in my core competancies nor my interest at this time. Perhaps you can build a convincing case for attracting a designer of some level is work with you, this will likely be done on a personal level. You have some convincing work to do to demonstrate that you have the business skills to partner and complement the work of the designer. Good luck.