Have you tried just using Jira for this as well?

* "First-class item" => Make a custom work-item type for "Requirement"

* "have comments attached" => Jira comments

* "Generate a task/see tasks completed" => Add items as sub-tasks

* "Version control" => Jira history tab

* "Bugs filed against req" => New issue, link to Requirement

Confluence also has pretty good integration with Jira if you want to write longer/formal documents - you can link to Jira items and the wiki page will update the status of the item automatically.