You can check the Chatty Couchapp Tutorial app from Smileupps App Store
It's a pure couchapp, relying on CouchDB only as its backend. The tutorial is still work in progress but the couchapp is fully working and you can download its source code.
It implements role/user based read/write ACLs using a single CouchDB database. This way you don't have to setup N replications where N depends on the number of your users. You only have one database containing all your data, easy to be queried on the fly(with temporary views) and for maintenance operations. Of course you can decide to increase the number of database, depending on type of your data and use cases.
A single couchapp contains all the necessary code for frontend, admin dashboard and server side API implementing business rules
The user, depending on his roles have different access to different sections. i.e. he can access the frontend website, but not the admin dashboard.
You can install the free trial, then download the source code with Smileupps deployment tools, change it, upload it and check your changes.