The most important changes would be that

- Uber has to take on a lot more of the associated risks (in practice that means paying a lot more insurance)

- Uber has to pay benefits to their drivers and ensure that their hourly wages meet local minimums

EDIT: Or, Uber has to change the way it operates so that it can continue to treat its drivers as contractors.

Theoretically very little. There's a decreased profitability, but not much else. Presumably their tech was what set them apart, and so it shouldn't matter whether their drivers are employees or contractors.

In practice, their entire business model is built around externalizing all their costs and shoving them onto their drivers.