I would buy such device, but with better components, design and build. Yes, it will cost maybe 500 eur, but I'm fine paying - I could ditch my personal laptop and just use DEX from my phone, keeping everything on single device.
Yes, people say you could buy a crappy laptop for that price - but that's the thing, I want premium extension to my phone and not a crappy laptop. Current offers from uperfect, nexdock are not good enough - basic displays, bad speakers, week battery, bad trackpad..

Love, Love, Love the idea!!! I just need 18" version of it with a bright screen and a comfortable (like original ThinkPads) full-size keyboard. And if I could RDP from it (maybe, with help of some very simple CPU), that would be the best!