This feature has now been implemented as of SketchUp 2021.0 :
Release Notes: What’s New in SketchUp and LayOut 2021.0?
Direct download updates
As we are releasing more frequent updates to SketchUp, we want to make it easier for people to access the improvements we make between ‘major’ versions. In this release, we are introducing a direct download update. This means that the next time there is a new version available, you can use this update service to automatically download the proper language version. When an update is available, you’ll receive a notification in SketchUp. You can initialize the direct download update at that moment, or defer to a later date. After downloading an update, you will be prompted to save and close existing files so that SketchUp can shut down. From there, you can install the update to the desired location on your computer.