[Vytis]

If I understand you question correctly here's what I do all the time:
- Once your replacement music comes in: Import Session Data > New Track(s)
- on your Draft/temp music tracks create new empty playlists
- Drag your new music to the empty playlist on your old Temp music tracks. Make sure 'Automation follows events' is deselected.
- Adjust clip gain if overall loudness differs old vs new track
This way you retain any automation you've created on the temp music and can easily switch playlists between old/new music.