Kinda precludes you from using roundcube though?
Even properly integrating with a mysql database isn't clear - password changing didn't appear integrated and fixing that wasn't obvious?
Overall SOGo looks like a nice "enterprise class" solution. Nearly went down that route except that I needed roundcube for some lighter weight installations and there is some advantage in keeping the same everywhere. Personally if I could get the Kolab calendar, contacts and notes applications working with my caldav/mysql backend I would be done!