Your a priori success-rate of 85% is hard to manage and 5-10% annually in return is too low for that risk. I can invest in opportunities with a higher return on equity and have things better under control.

But your scheme is flawed in just another way: You invest in the entrepreneur, but you don't profit from his success. You're just granting a credit (% on capital), not making an investment (% on performance).

And there alread _are_ such schemes, where investors can give money to high potentials and profit from their later income. These high potentials have to take a life insurance for the case they die in the meantime...