Sounds like you are doing what we are doing. Testing the waters, evaluating how NoSQL technologies fit into your architecture, and testing your problems against NoSQL solutions.
I'm still a bit wary of using NoSQL, and we store document revisions (e.g, if I modified invoice 1021, the lastest version would be updated in SQL, and the last version would be pushed into NoSQL) into SQL just in case (by using a draft_id column).
We need to see if our software is still deemed auditable by accountants since they have very strict guidelines on how a document trail should be stored.
It is refreshing to see the approaches.