That is what's happening today, offered by the only company with the scale to do it: Amazon (It's called FBA). Then when they see your products are selling particularly well, they stock them, undercut you, and put you out of business.
Amazon have a lot but are a long way off having everything. Health and Beauty for example, they may have the top 50k sales ranks pretty well covered but at least the top 100k are probably worth a middle mans time.