Have you looked at Drupal? Drupal 8 with a couple modules could handle everything you need(custom content types, discussion boards, blogs, user profiles, etc) It is scalable and easily configurable. www.drupal.org plus the community is a big help.
We looked at Drupal 8 a little and spoke to some people in the organization who are using it.
Our concerns are:
1. the need for full-scale developers when working with Drupal. We don't want to the site maintenance to be dependent on hard-core coders long-term, since that requires always hiring programmers rather than lower-level web developers.
2. Drupal upgrades. We've heard that it's very difficult to upgrade between Drupal versions, as many of the plugins/modules don't get upgraded, at least not right away. So you can be left with a Drupal site that can't be upgraded without losing functionality.
Any comments?
Without bashing it too much the main issues were severe lack of good documentation, bugs in the core, bugs in contributed modules and poor development workflow.
Funnily enough, as a result of this project I started investigating alternative cms's and from now on will be using Craft.
Initially I was concerned it wouldn't be suitable for a project as complex as the project above, so I spent a day or too recreating some of the more complex parts of that project with Craft and it was a dream!
The developer learning curve with Craft is one of the best I have ever seen with a cms. We now have devs who previously only did frontend using craft in no time.
Nothing but good things to say about it really!
Another option may be Backdrop (backdropcms.org). Which is working on maintaining backwards compatibility.