The hard parts are:
1. capitalization - once you have investors who have more say than employees, it's no longer very cooperative
2. legal - the structures for for-profit or hierarchical non-profits are well defined and there are any number of experienced law firms that can help structure a business, while for a cooperative not so much
3. structural - there are a thousand books published every year about for-profit businesses. There are comparatively few about starting and running a cooperative. Although the latter have more signal than the noise of the former.
These aren't insurmountable problems, though. They've been solved before.
| Amazon as a coop
A cooperative Amazon would probably work best as a federation of cooperatives.