A new standard – headset, bb, axle, wheel size – take your pick.
I like the usb powerpack idea. Some way of keeping it waterproof while on the move – speaking as someone who has just killed a garmin and power pack on a long wet ride (as has a friend it would seem). I’d make the battery part of a garmin mount and some how box it up in one package.
Some sort of modular saddle bag arrangement so that a pump/tool/tube all clip together as one neat package.
I did see one that I would buy which was a bike saddle bag that also doubled as a small bar bag or would go in a bottle cage as a tool bag. One item, multiple uses. It was basically a small cylinder with clever strapping.
Not sure on other inspiration but gravel biking is now popular so something for that market. Commuting is also big but then your options are probably covered there.