Clipboard problems

A problem I stumbled upon is... how to handle copying and pasting? Copying a single clip is no problem. Copying a piece of a track isn't problem either, I only have to store the track beginning offset and copy the clips' data.

However, how to handle nested tracks? Should I group tracks by video and audio?

I remember when I used Premiere a while ago, I could add audio and video tracks. What I don't remember is... would I add only audio tracks or video tracks? But it seems You could add audio-only tracks, i.e. for adding background music to a video. Therefore, tracks shouldn't be grouped by video and audio.

How to handle then copying and pasting?

Here's an idea. Do a copy of the current timeline in case of multitrack clipboard, and paste into exactly the same tracks (no up/down possible). I'm thinking that this would have the same effect than dragging and dropping a selection. However, how to move multitrack clips up/down? I think I'd need to add a command for shifting up / down clips.

When I figure out how to solve this, I'll be able to implement cut/copy/paste effectively.