Hi Emil, 

Can I ask, are you building this just internally - in other words are you looking to build this just for your own use, or are you looking to build this to sell as a Software package?

Either way, what you are describing is basically already heavily available on the open market. I wouldn't bother building it to be honest, but merely pay for licenses to either TFS by Microsoft or Alssian Jira and Confluence.

Both are very good tools which do all of what you have outlined above. My personal choice would be Alssian JIra and Confluence (two different packages made by the same people, which inter-link with each other). 

Jira is the User Story/Development tool which helps explain the requirements and development side of things. It also is heavily based on Project Team communication and interaction. Confluence is more a wiki type product, which is aimed at the Project Team members (including Devs and Testers) writing notes to share with each other and other people outside of the project team on how things work, why decisions were made etc, That's especially useful if you need to update a process or system 5 years on - no one will remember what you did and why you did it, but hopefully your confluence notes are good enough for you to read them and then understand. They can be set up a multiude of ways, including Kanban Board and Backlog views.

TFS is aimed more at the Developer than the Project Team (i.e. BA and Project Manager), but can be used by them to write up User Stories, Features and Epics. It doesn't have the all round appeal that Jira and Confluence has, but tends to be available in many Standard Business Desktop packages from Microsoft. 

Jira and Confluence you have to pay for a license per User, but is, in my opinion the better of the two. There are plenty of other packages available as well. A good internet search should find these for you.