Respectfully I disagree to an extent. Why expend the effort on a solution to something that doesn’t need to be solved?
It’s entirely possible we are on the right track already and that a look that matches with current visual expectations is what everyone wants, in which case end of discussion. I am merely asking a “bigger picture” question so we know why we have certain expectations and goals.
With a single chromaticity and no relationships to maintain, presumably it would just map to display max (255,0,0).
Now of course what happens when you add different chromaticities at different luminance ranges both within and beyond the display range? If you are attempting to keep scene “intent”, then in my mind it should be chromaticity-preserving with compression of the luminance only. Because scene luminance is potentially unlimited (especially if computer generated), you would have to specify an upper threshold/clamp to keep a realistic ratio of the values under the clamp, which also gives you a ceiling to map all values equally. Looking at the “red christmas” example from Chris’s post it appears this is more or less what the current ACES transform is doing: it is trying to respect the chromaticity of the scene-referred data. However, it is clamping too quickly and just clipping a lot of potentially useful data.
The “naive drt” and other transforms like IPP2 instead of being chromaticity-preserving follow a “path to white” where high luminance colors instead “burn out” to white to mimic what happens with film. It’s generally a pleasing look and what we are all used to seeing in film, but it’s also not realistic.
There are plenty of cases where aesthetically pleasing can trump “technically correct”; I’m just trying to have the conversation.