I have now released v0.9.3.
I've made the neutral tone operator more flexible on the rolloff parameter so it can be specified per hue. I've seen advantages in subjective profiles to have a shorter rolloff for the skies range, and a longer rolloff for the skintones range. This maintains better sky color in landscapes, and render high key portraits with a more pleasing and nautral-looking transition to the whitepoint.
Then I've digged deeper down the Capture One converter and added some features required for making general-purpose profiles that work in the same way as their bundled.
C1's profiles are a bit messy, it seems like they apply the tone curve separately, which they do, but the also have a residual curve in the LUT. This means that "Linear Response" still means that you have some residual S-curve left. The purpose of this as far as I can tell is to minimize the RGB curve color shift. The separate curve is never a true "S" so it doesn't distort color as much, and then the LUT curve is probably added with some other technique, perhaps a Lab Lightness curve. This split approach makes the profiles work better than they otherwise would with different curves. It explains the mystery howcome C1 can produce good results despite using RGB curves as tone curves.
You can now design this type of profiles for Capture One using DCamProf, by following the workflow described in the docs. It will then get its look optimized for the default curve, but will look ok with the others, just as native profiles. Perfectionists should still design one profile per curve, as always.
What still may be left in terms of C1 support is gamut mapping. DCamProf currently doesn't do any, meaning that high saturation colors indeed get high saturation and may clip. There are ways in C1 to get them in gamut again but it seems like their approach is to have gamut compression in the profile itself. Context sensitive dynamic gamut mapping is a zillion times better of course, but the 1990s way to do it was in the profile, and it seems C1 is still there :-/.