An obvious extension to having a coupling rating system is having tools to automate the rating. Some of the newer web service management tools allow one to create an inventory of the services on the network. These tools are designed to help manage what you currently have rather than optimize your go-forward design. Design and architectural issues in web service infrastructure will first surface at the macro level.
In our recent architectures, 'ilities' emphasized responsiveness, availability, scalability and reliability. The 'ility' (non-functional requirement) of choice in the SOA will be Agility. The materials and the structure that we use to build our systems will have the opportunity to be nimble. Agility is not automatically granted in an SOA; it must be part of the plan.