For internal reporting, it would be nice to be able to filter reviewed Ideas list to show which were promoted to create a new feature and which were rolled into existing features. This would allow me to identify what are related, but not necessarily merged ideas.
We recently rolled out the ability to link any record in Aha! with one another. This would allow you to show relationships between different records in Aha! You can use this for dependencies as well as basic relationships. You can access this by clicking the Actions menu on any record and selecting "Link to another record"
Based on what you are describing, it seems like this might be helpful to you to identify and show when idea is related to a feature (as opposed to a brand new feature being created based on an idea).
While we don't have separate filters planned, you might consider this workflow. You can read more about this capability here: http://blog.aha.io/universal-dependencies/