Yes, I guess the main reason it has still not been done is that there is not enough interest by enough people.
There are basically two different ways that you can follow, and both are not ideal:
You can either use the original controller and the original connectors and try to emulate the original protocol. That's what Symbolics founder MMcM did. And what you get is a keyboard that in most cases has 1KRO, very few modifiers (unless you have a LISP keyboard probably
), and no key up detection.
Or you decide to replace the old controller with a modern SoC, which in most cases means you need to destroy the old controller ... and who wants to do that on a 1970s keyboard?
IBM did us a great favor when they separated the keyboard PCB from the controller PCB in their beamsprings and most of their Model Fs. Micro Switch unfortunately did not do that.
Bottom line is no one here has converted any Micro Switch HE keyboards (except the LISP guy with the Symoblics collection but let's ignore him for now), I would never assume or assert it to be an easy task. 