Would it be much trouble to add an option in the file browser context menu to replace the current playlist with the selection, rather than just inserting or queuing? Currently the only way to achieve this is by stopping playback, then inserting the new tracks into a new playlist which 'replaces' the existing one.
I quite like having whatever is currently playing continue to play whilst I look for something new to listen to, and stopping playback when I've found something means I get returned to the menu, and then have to navigate back to wherever I was before I can create the new playlist.