Being able to adapt dynamically to schema changes would be great. If you do develop a solution for that, please do publicize it. Simple uses segment.com for some communication of analytics info to third parties, and Segment folks have built some capabilities to infer schemas from incoming messages which they then apply to history tables in Redshift. We're hoping to learn more from Segment about how they make that happen.
What you described with documentation efforts is kind of scenario I fear. We could spend significant effort putting together a documentation system that simply doesn't meet a real need. It's good to know other folks are also struggling with that, though.
We're very interested in trying AWS' new Database Migration Service to see if it provides a nice, automated way to get a mirror of the source into Redshift. https://aws.amazon.com/dms/
What you described with documentation efforts is kind of scenario I fear. We could spend significant effort putting together a documentation system that simply doesn't meet a real need. It's good to know other folks are also struggling with that, though.