I believe they are planning on some rework here... (and hopefully it's copy of latest Vray).
But here is quick and painlessly easy to implement semi-solution without affecting current VFB in any way at all.
Let's just add parametric mode to existing point-mode to Curve like in Adobe ACR. Because the parametric sliders in ACR are basically just doing the same thing as the parametric mode of the tone curve.
Yeah but the saturation.. let's just kill that one and bring in proper Vibrance (or do the Vray and give everyone everything)