Ok, I wrote it 
You can download the first plugin prototype here.
It still requires some configuration - basic knowledge how to install a plugin, changing the tools and shortcuts in it (right now they are just embedded in the code), and removing the shortcuts set in krita normally (they override my plugin)
Here is the list of all possible keys to map, and all the actions can be found using ctrl+f here (do we have some better place with all the actions online? I couldn’t find it on scripting school).
Overall it feels nice to use (much better than I expected), though I tested it only for a minute or two on linux. There are some problems when releasing the key when other modifiers are pressed, but nothing serious so far.
Maybe I’ll even work more on it in the future - double press of the key to switch permanently to a tool, or go back to paint tool (if the tool is already selected) would be great. For now it always goes back to paint tool - it could remember the recently used one, but I think its not very needed…