Two models I'd like to add to this as examples that this is actually possible with all form factors:
First the The HP Elite X2, a Surface Pro-class tablet. Quite analogous to the EliteBook - sadly the RAM is soldered (IIRC one of their first actually still had a SODIMM slot):
And second, the Fujitsu Lifebook U93x. smaller and lighter than most Business-Ultrabooks -
almost MacBook 12 size/weight, but still KabyLake U, >10h battery and everything socketed+lots of ports (including USB-A, HDMI, even full size Ethernet!):
This tablet is absolutely fascinating; it turns the "cost of repairability" of a pro-tablet into a material measurement : 100g on 700g (14%).
I wonder, all things being equal (which of course, it's not realistic), what's the impact on the attractiveness to the general (not HN) public. It would be significant even it if would conquer a "solid nieche".
To make an interesting comparison, a 12.3" Elite X2 weighs as a 15" Surface Book 2 (though the latter has a different form factor, while stil being in the pro-tablet category).
(~700g is the standard weight of a "pro-tablet": 12.x inches, without (cover) keyboard)
Indeed, this is something I've wondered myself, since in my experience even 100g does make a big difference in a tablet.
But I've come to the conclusion - it's hard to really pinpoint the "cost of repairability".
Taking the numbers:
IPad Pro 12,9: 692g
Surface Book 2 13: 719g
Surface Pro 2017: 770g
Elite X2 1012 G2: 800g
Surface Book 2 15: 817g
Of course, the IPad pro shines, and apple certainly are famous for "shaving off every possible gram" - but it's just so different a platform, esp. thermals, that it's hard to make conclusions towards "cost of repairability".
The Surface Book 2 tablet modules are light for their size, but I'd say this is primarily bought due to a significantly smaller battery compared to the SP and the Elite (23Wh vs 46/47Wh) - batteries are heavy.
The only devices here realistically comparable IMO would be the Surface Pro and the Elite X2.
But IMO the more interesting device I've posted for this kind of comparison (even though I wouldn't consider +/-100g that critical here as I would with tablets) is the Fujitsu U937, because it's one of the lightest x86 notebooks overall on the market, while still offering competitive specs in all metrics (CPU, RAM, ports, battery size, display size, etc.) and still being easy to repair/upgrade.
(Too bad that keyboard and touchpad are rather mediocre :( )
First the The HP Elite X2, a Surface Pro-class tablet. Quite analogous to the EliteBook - sadly the RAM is soldered (IIRC one of their first actually still had a SODIMM slot):
https://ifixit.org/blog/8135/hats-off-to-hps-repairable-tabl...
https://ifixit.org/blog/9309/hp-elite-x2-1012-g2/
And second, the Fujitsu Lifebook U93x. smaller and lighter than most Business-Ultrabooks - almost MacBook 12 size/weight, but still KabyLake U, >10h battery and everything socketed+lots of ports (including USB-A, HDMI, even full size Ethernet!):
https://www.notebookcheck.net/Fujitsu-LifeBook-U937-Core-i5-...