FYI, to avoid any potential confusion above, I don't work for JRiver, I'm just another user like you. Bob, however, does work for JRiver and is one of the JRemote app developers.
That said, I can tell you that JRemote does exactly what it's designed for and there's no shortcomings in its initial design as you're assuming. It's not meant to be a general purpose media player app that supports import and playback of local media, it's only meant to be a remote app and requires JRiver Media Center running on another device like a PC or Mac in order to use it. It's purpose is to either a) use it was a remote to control JRiver Media Center running on a PC or Mac it's connected to or b) allow media to be streamed from a JRiver Media Center server to the remote (e.g. playing music from a JRiver Media Center server to JRemote on your phone) and that's it. Making it into a general purpose media player app is completely out-of-scope for what it's intended to be and I don't honestly ever see JRiver adding local playback functionality to any of their own remote apps. I would be HIGHLY surprised if they ever did that as it makes no sense at all. This applies to both JRemote on iOS and JRemote2 on Android, along with Gizmo on Android and Panel in web browsers. The only JRiver app that supports local playback of media is JRiver for Android.
Unfortunately you'll have to use multiple apps to achieve what you want and I suspect that's not ever going to change.
