Well, I suggested 2160x1440, just like in Surface Pro 3. 2140x1440 isn't exactly 3:2, it's just approximately similar.
Surface Pro 4 uses some weirdo resolution 2736x1824, and I think a 16:10 panel with such non-standard height would be very hard to find (if it exists at all). I think we should choose a physical panel resolution that is available, instead of the resolution that we want in 3:2 mode (if going my suggested route). You can see a list of resolutions here: https://en.wikipedia.org/wiki/List_of_common_resolutions
Basically, we can have any of the 16:10 resolutions on that list, and then a 3:2 resolution with the same height. If we're going this route, we don't need to use any of the "standard" 3:2 resolutions - we are free to set whatever we want as the resolution, but it's best if the height is the same as the chosen 16:10 resolution, to prevent Windows from messing up the desktop (as I said in my initial post) and the GPU from upscaling it to fill the screen's physical height (which reduces video quality).
So for example, if we take a 5120x3200 panel (which would be expensive, btw), we can have a 4800x3200 resolution when in tablet mode. But I don't think we should go this high in terms of resolution. 1080p on 11" is crisp enough for me, I mean I don't hold my device in 10cm from my face so I would be pretty happy with what I suggested before. Or 2560x1600, which would translate to 2400x1600 in tablet mode. The latter one is pretty widespread in 30" desktop monitors, and the Nexus 10 has this resolution, but I couldn't find any devices with that one in similar size to the PF.
If we go with a 16:10 screen, the device will need to have a 1cm physical bezel, and shrinking the working area to 3:2 would provide extra 9mm of it. As I said earlier, that's the perfect bezel size for me. What do you think, guys? Or we could also go with a 3:2 screen and the North Cape approach, where the bezel is also added on top, but that would create the problems such as where to place the camera.