Many times it happens that client want to achieve a lot within a specific time but does not have resources on his side to continuously monitor and provide feedback. As a service provider we can deploy more of BA's (Business Analyst) to help us, but no amount of BA's can resolve the bottleneck on clients part.
In software industry we have ratios of dev/test, dev\lead (module, team etc), i believe such a ratio should also be there for client. Imagine a team of 20 developer churning out code with only one client frontending. Having multiple client personal to help the development team would help in such scenarios.
This approach may have it's own challenges, such as deciding who has authority, how are responsibility divided between all etc. These issues can be resolved with clearly defined roles, responsibilities and domain for the people who are involved.