They are themselves abstraction layers for the apps that are made for them. Software has many levels of abstraction from what you see on the screen all the way down to hardware.
The only thing is, the refurb market can't be that great to pay for this change. You might not think it, but changing to better screws and adding the metal threads is crazy more expensive.
I still have my white 701 that I put a black keyboard on and soldered in a Bluetooth module. Some of the most fun I've had using a computer and I wish the form factor was still a thing.
Because in situations like this, segregation is a good thing. You don't want automated tools futzing in directories that you might have wanted to keep as-is.
For #3 and for people that might not have sodium citrate handy, adding a slice of American cheese to cheese sauces will do the same thing as there's plenty of sodium citrate in there to go around.
They are themselves abstraction layers for the apps that are made for them. Software has many levels of abstraction from what you see on the screen all the way down to hardware.