Interesting. Sadly, I believe the Photoshop approach would not produce a DNG file that you could normally interpret in a raw processor of your choice. Looks like pixel shift cameras (which apparently still use Bayer sensors, just moving them around, to debayer at capture time so to speak) is the most practical option at the moment.

I’m curious if it is technically possible for a digital sensor to capture the entire light spectrum of the scene, without the need for RGB separation at any stage—similar to Lippmann plate[0].

[0] https://en.m.wikipedia.org/wiki/Lippmann_plate

There are Sigma cameras with a Foveon sensor that can do it:

https://en.wikipedia.org/wiki/Foveon_X3_sensor

Though they're not as good in most other dimensions as conventional Bayer filter sensors (most Amazon reviews e.g. say that it's impossible to photograph moving human subjects without daylight iirc).

I looked at Foveon before, and got the impression that it still effectively relies on RGB separation/recombination, though in a more elegant way than Bayer sensors. (That said, Sigma’s doing some really cool stuff.)