Before they can implement 3), they have to actually make ChromeOS scale nicely to high-res displays. I've got a Chromebook Pixel that usually runs at slightly below 1080p (closest possible with 3:2 ratio) despite having a max of 2560 x 1700, simply because the max res is unusable in Google's own OS without a massive amount of tweaking. UI does not scale, taskbar does not scale, have to manually bump up the font size within Chrome, etc. It's embarrassing.
And I say this as someone who really likes the Pixel otherwise.
I'm posting from a ChromeBook pixel running at 2560 x 1700, and the UI looks great. The taskbar, UI, fonts, etc. are all scaled perfectly.
Have you tried running at 2560 x 1700 on the most up-to-date version of ChromeOS? Some of the issues you had may have been fixed in more recent Chrome releases.
I'm posting from an Acer C720 docked to a 1920 x 1080 Benq monitor, and it looks and works just fine. If Open Office was working on ChromeOS, my joy would be extreme.
Which goes to my point - that it would be even easier to do 3) on Android, than it is to do it now on ChromeOS, since Android has nice resolution scaling.
And I say this as someone who really likes the Pixel otherwise.