I recommend to cut every corner you possibly can when doing short jams like these. Don't make your own camera, just extend Cinemachine since it's a super good tool for easily customizable camera movement with lots of built in stuff like smoothing, camera shake etc. If you don't know how to extend it properly, you do the next best thing you do know how to do. Toggle on and off GameObjects! Use one cinemachine camera for the play/launch section, and just use the normal camera with movement and zoom for the building part.
Think like a lazy programmer.