Customizing keyboard shortcuts has been discussed before but never gained any traction.
Addons exist to perform the same function, but break in certain situations
Having native shortcuts speeds up review quite a bit. External solutions like AutoHotKey can’t be context aware (like a given hotkey may have a different function on the the front of the card than on the back).
For a good example of OSS with extensive hotkey customization see Subtitle Edit, which has a much more complicated interface than Anki, but allows hotkey customization of almost all functions: