You're looking in the wrong direction, you can always add a trivial trace of some additional wavelength and have no measurable effect on what people experience. That remains true no matter how many finite sensors you imagine they have. That part is simply not interesting.

What's interesting is differences in the MINIMAL set of physical things that need to be detected to get the experience.

The objective truth is that if I hand you a machine that generates just single wavelengths of photons, you can cause "Normies" to say "yellow" but you can't do the same for "magenta".

That asymmetry remains even when you talk about adding more sensors. You can frequency-shift an R/G/B cone to get a new kind that "peak-triggers when normal people say yellow" but you cannot do the same to create one which "peak-triggers when normal people say magenta". You would need to create a fundamentally different kind of sensor.