I'm not sure whether in a forum setting it would be easy to enable the document control described above
It depends on what you want at the end of the day. You are talking about providing a commercial service, so you will need to provide a safe, secure and accessible environment for your customers.
I would suggest that you take a look at two things -
1. Versioning of documents and how that could be provided. The problem I see with using forum software is that the only way you can recover a document, irreversibly changed, deliberately, or accidentally, by a user would be recovery from your R1 Soft Backup. Provided this is incremental, say 1 hour snapshot, you could do this. If the backup admin is really good, you could probably do a file recovery in around 15 - 30 minutes. Experience tells me that this will not be a rare event. Users make changes without thought and often without any idea of what those changes may actually do.
Versioning means that the users, or their local admins, can make previous versions live in seconds, so the facility makes sense.
2. EDMS is usually either Database containing meta data and a link to the document store, or Database where the document is held as a BLOB ( Binary Large Object). If you use the latter, you have fewer problems as the link between the meta data and the document can never be broken, they are effectively the same DB record. In the case of the former, experience tells me that a major headache will be mending broken links. You will need to allocate 365, 24/7 admin support for this. Also make sure that the EDMS structure is robust enough to disallow a user from saving a document record when the actual document fails to store in the document cache. This happens more often that any EDMS provider will admit. The users believes that the document is safely tucked away, when all they have is a meta data record containing a link to a none existing document.
You will also need index crawl and a first class search engine. Users will lose documents and even forget what they filed and where they filed it - but that's the same when they use any computer filing system.