Unfortunately everything would have to be resized. If you use GIMP you can bulk resize the gauges. What I do when resizing is make a large template with the preference section. If it helps here is the background I've resized to 480x800.
The assets are not hard to resize GIMP can do bulk resize so I can do all gauge instances in no time but you're right sometime you're just better off starting from scratch.
Check your preferences (see photo https://photos.app.goo.gl/pz8gZL6JzZScvFwP9
I imported the download and it sized fine Try this one https://drive.google.com/file/d/1gD_vHUjGH-RzdmtK4IYCro3WpwxrqR-J/view?usp=sharing
That is from my personal file