The addition of HSL controls for the adjustment brush and the gradient tools would be a wonderful advancement and offer LR another great feature set that I'm sure would come in handy for the vast majority of Lightroom users.
Adding HSL Masking sliders as an alternative to the color point selector in color range mask, simillar to HSL Secondary in Lumetri/Premire Pro.
The color range is a great tool, but when batch editing shots where the color point moves it isn't ideal. Being able to mask with HSL Sliders as an alternative of having the color picker automatically adjust HSL sliders would be more useful I think.