A feature audit is a process to figure out the list of the features you want to develop and they matches with the list of the features your customers are asking for based on their requirements. The final list if what you want to work on but you are sure that your customers need those features in the first place before you even start working on the plan for that particular feature.
In MyProductHub we have Ideas (a Feature or a set of features) which can be arranged as Themes. Each Idea is divided into smaller iterations which can be mapped to a specific user story. Iterations can further be divided into user stories if required to handle it in smaller pieces. Using the feedback section, you can map which features are desired by your customers and which features makes more sense to be prioritized before any other features in the list.