Assembly line workers shouldn't just do the physical job: Ford should listen to them. When it comes to improving quality and safety on little things, workers know better than engineers, and they cost less. (Maybe Ford now listens to them, I don't know, but the philisophy that a worker should only be paid to work instead of thinking is what created a gap between most Japanese and American products.)
Where I work (part time), we constantly give ideas to the supervisors on how to improve things, and guess what.. they don't listen. When it's their turn to implement things, it never works. All-robots plants work in some industries, like metallurgy and chemical plants, but not in the auto industry. They cost a lot to implement, to maintain and to repair, and if there's a recession, you still have a lot of fixed costs to impute on less production. Nevermind the bad press you get for not hiring lots of people: believe it or not, having tens of thousands of workers on your payroll gives help when negociating with the government for subventions, and families of workers tend to buy your products.