- Keyboard (e.g. if Purism can source a keyboard with a middle nub (ala ThinkPad)
This is sadly trademarked by IBM, who gave the trademark to Lenovo, who sometimes licenses it to other companies.
- CPU
This is unfortunately soldered into the motherboard, so you’d need to buy a new motherboard.
- Motherboard (to support 32GB of RAM)
I think this is dependent upon the sourcing of the motherboard. I’m not sure about if that is possible.
- Touchpad
If I remember correctly you can replace this easily, so as long as you get a touchpad that fits the size requirements and works with whatever OS you’re using, it should be fine.
- Display
Also possible to replace.
I also made a post here that might help you.