The story goes...

On premise SharePoint 2010 with external access
Remote users had a plethora of upload, check-out issues
Desired a wiki
Tried (2013), wiki still just the same as 2010 and document management issues worse with OneDrive for Business
So, back to on premise with documents in SVN (remove users are happier with document uploads working and "check-out" managed by SVN pessimistic locking)

So, what I was thinking was perhaps synchronising SVN documents to on-premise SharePoint (DMS in SharePoint on premise is still very good)?