I'd love to see a custom command that allows you to insert or overwrite a highlighted clip from the project panel but only insert the video if audio and video are embedded in the clip or just the audio.
This is a feature that FCP X has and is an immense time saver when adding broll to a project. Premiere pro does allow you to click and drag from the source monitor panel only video or audio but it's mind blowing they don't have a shortcut for it.
Depending on how it would need to be implemented it would be good to have 2 variations of the shortcuts. One for a highlighted clip or clips in the project panel that honor in and out points marked in those selected clip(s), and another for the active clip in the source panel that also honors the marked in and points for that clip.