There definitely needs to be a very powerful reservation system. Some high-paying members might be able to rent out certain pieces of equipment for days at a time, while others would only be able to access it when vacant. You would not want somebody monkeying around with your C&C machine while you were taking a 2 hour break.

It would certainly require some good software, and community support. Maybe the different pricing levels would allow you to book equipment further and further in advance, to ensure availability for big projects.