WAN Enterprise IP and Network design???

I have a client who is considering a WAN with 600 to 2000 locations. Each location will host a server and 10-60 nodes. The network will most likely be Wireless Ethernet with Cisco equipment. The bandwidth,the type of circuit, and the cost, and scalability are all factors? This scale of network may need an SLA with a telco provider? If so how is that best setup? What is the best way to design and provision this network with IP’s? Where would you start and how would you do it? Any links or suggestions are greatly appreciated.