Martin Edström has announced a new package: massmapper. The idea is to make it easy to—for example—copy all the Ctrl– bindings to Super-. That’s a real pain if you try to do it piecemeal by hand but massmapper makes it easy.
The above is pretty much the TL;DR. To get a better idea of what it does and how it works, take a look at the README from the GitHub repository. That lists all the commands, which gives you a good idea of what’s possible.
There’s a lot of dark corners in this enterprise and judging from the README, Edström has considered them and either made allowances or documented the ones that can’t be fixed. An example of that is Ctrl+g, which is hard coded in Emacs and can’t be changed. There are a few other things like that but mostly it “just works”.
I’ve never felt the need for mass rebindings: indeed, I don’t think I rebind any keys but lots of people appear to consider it an important part of making Emacs work for them. As usual, Emacs lets you have it your way. In this case, not directly, but by making it possible to write a package to do it for you.