Mediasurface, Stellent, Documentum and many other vendors have successfully decoupled their repository search capabilities from their underlying CMS. Other observers have asked for decoupling of other services like security, and I have often seen customers asking if they can use their own choice of workflow software, version management software, and so on, instead of using features embedded in the CMS. Using best-of-breed products to build a system is good in theory. For it to work though is quite difficult using today's products. Most of them have proprietary and tightly coupled ways of doing things, either due to legacy architectures or competitive differentiation. To allow decoupling (or even loose coupling) of services, most of them would need to re-architect their products. Also, for decoupling to work, standards play a very important role -- not just CMS products but the whole ecosystem. So if a CMS supports decoupled version management then 3rd-party version management systems also have to adhere to standards. Until this happens, you need to take a balanced approach to deciding what should be decoupled. If you require many 3rd-party services, most packaged products probably won't right fit for you.