I wish I had the money and the know-how to do things like that. In a world where many companies are downright hostile to user needs and preferences, we need more DIY electronics — not less.

It's never been a better time to get into DIY electronics projects. Literally every part of the process is well within a curious hacker's abilities. Microcontrollers and cheap sensors/displays started becoming commonplace around 15 years ago, and the most recent innovations are good and cheap PCB production and 3D printing your own parts/enclosures.

You might check out https://hackaday.com/blog/. They quite often feature projects from people who built the thing they wanted, instead of buying it. (Often because the thing they wanted couldn't be bought in the first place.)

Hot air rework isn't that difficult. It's a skill like any other.

Only thing that's expensive is you breaking the mouse in the process.