4k with 2x upscaling would be identical GUI sizes as the 1080p display shipping in the librem 14 without needing fractional scaling. Also software is software and can be trivially replaced[1], but I can’t download additional pixels.
[1] For example, I use sway which supports fractional scaling.
I’d be happy to buy the 4k screen as a separate additional purchase and install it myself if it was shipped as the full display assembly. I’ve already replaced the screen on my xps 13 multiple times.