Add some features to our Windows 8 Mobile App

We have an app that converts Youtube videos at our server and downloads the song as an mp3 file to the phone. We want to add the following features to the app: 1. Add support to download the video itself from Youtube, with the option to select the quality of the video (depending on the available qualities for each video). 2. Modify the audio player in order to support playing video, currently the app has an embedded player which can play mp3 songs. 3. Add the option of creating playlists. 4. Limit the download of videos to five downloads per day, with the option to unlock unlimited downloads with an in app purchase (this feature is already implemented in the audio part, so you will only need to recreate it for video with minor modifications).