I think if you can make your model work with a competitive APR then you'll take over the world. At 20% APR I would guess it's just not worth it for the majority of businesses (ourselves included).
For businesses that expect a slow payback, the APR isn’t nearly that much.
I’d use it to reserve EC2 instances, for example. I get a 40% cost reduction on AWS over 3 years, and I’d expect to take that long to pay back the capital. The APR would be fine in that case, and I make 20% more than I would otherwise.
That's a great idea!