If you can find people freely willing to provide labour services at the price you offer, I see no problem. As far as "forcing" farmers to earn less, how are you going to achieve that? Coercive appropriation of goods is a practise strongly restricted in modern capitalist societies. Finally I highly doubt there is a good market for unsafe food products, though I am sure for some people it would be an acceptable risk - if you are discovered faking the quality of your food products though I imagine you would go out of business pretty quickly through the standard feedback mechanisms of capitalist society (the media, consumer outrage).
Doesn't sound like a very strong business model to me unfortunately.
Before Uber can righteously challenge European legislation, they should prove that they have ways to address the issues that generated that legislation in the first place: are all drivers insured? Are their vehicles safe? Etc etc.
Why can't we simply let people decide for themselves whether they want to ride in insured vehicles or not? Are people too stupid to calculate probable risks and rewards and make their own economic decisions?