How would this system work though?
I'll go back to my personal example.
I was hired at a contact centre for a webchat based job, where I was talking to sometimes 4 people at a time where other colleagues were taking just 2 at a time. I had the highest customer satisfaction rating in the building because I had meticulously worded my own custom scripts, and had the freedom to work in a way that suited me.
I left for maternity leave, during that time a much larger international company acquired ours and outsourced my department so they effectively sideways moved me to a call centre based roll.
For a while I struggled through, undiagnosed at the time, not sure why sometimes my words got stuck in my throat or I took long pauses or could only get whispers out. Didn't understand that I had selective mutism. Didn't know that the reason I was sat staring at a wall for sometimes 30 minutes between calls in what felt like a blink of an eye was because I was having shut downs.
My personal productivity had gone from twice all of my other colleagues to a quarter, because of a business change that I had no say in.
My role had changed not only in medium but department too so I had gone from having all of these scripts available to me for specific technical support queries to general customer service enquiries where customers could ask anything and it would be unpredictable, and I can not physically formulate language in the right tone, or in the right way to questions that I've not rehearsed. I got people regularly screaming at me for sounding like a robot because I couldn't formulate answers to their unpredictable questions in a non-monotonous manner, it absolutely sabotaged my self esteem.
I did end up leaving that job although they were well on their way to managing me out, but finding another webchat only job is extremely difficult as the industry standard for contact centres these days seems to be majority calls.
Businesses make changes all the time because that's how they evolve and grow and they have to alter their processes accordingly which I completely understand which is why I left. The adjustments that would benefit me ultimately would not have been reasonable for the business at that point in their growth, but I went from being consistently their top performing employee in the technology faults webchat department, making close to £1500 bonus each month on top of my wage, able to avoid a life away from benefits to their worst performing call centre operative, being assessed as not capable for work because the work I'm qualified and able to do just isn't industry standard any more.
How would it be fair to people like me who were employed for one job and were the best at that job, to finding things difficult, going through the arduous process of acquiring adjustments to level the playing field, who may have a reduced output due to no fault of their own and arguably the fault of their employer to receive less than minimum wage for the hours that they're working because the metrics are changed to being output based? It would disproportionately affect disabled people who can work with the right adjustments.