Reviewing the 

https://frame.work/

modular laptop, it's not much different than the others, very small screen, very bulky, no stated battery life but it's probably awful.  There was also the raspberry pi laptop, the OLPC laptop, the netbook revolution.  Laptops just can't be every high performing unless they're designed as 1 piece.

Lions believe the ideal way to get a modular laptop is a bare screen & keyboard with no computing in the lap part.  The CPU, RAM & storage would be a separate brick which would fit in a backpack or a pocket.  Maybe the computing could be a phone.  It would need 2 batteries.  It would drive the screen & keyboard over wireless.  There were wireless display standards 15 years ago, but probably nothing that can drive modern resolutions with a low amount of power.  Maybe something could be hacked.