In the seventies many harddisks were rented rather than bought. I came across one that when the customer wanted an upgrade to double the capacity, the engineer simply removed a screw so the head could access the whole disk area. Hey presto capacity doubled!
The same went for other features - I used to sell a typesetting system. One customer wanted a special feature and the engineer was sent to install - simples a small card that connected one part of the printed circuit board to another.
How times have changed.