I've been moving from obsolete color correction effects to Lumetri Color during past couple of months and I think that there are some minor improvements that could make it even more powerful for more advanced users.

1) Ability to rotate hue with color wheels. This is the biggest reason why I'm still using Fast Color Corrector and Three-way Color Corrector every now and then. Rotating hue should be possible with all color wheel in Lumetri interface (including HSL Secondaries). Also ability to set the target range (like Tonal Range Definition in Three-way Color Corrector) for each color wheel would be nice.

2) More curves. RGB and Hue-Saturation curves are a good start, but having a Luma-Saturation and Saturation-Saturation curves available would be pure awesomeness.

3) Ability to use curves (at least RGB one) with HSL Selections. Curves provides a lot more control than current tools available in HSL Secondary -tab.

4) This is just a personal preference, but i think that all changes that have been made in "Creative" tab should be applied between HSL Secondaries and Vignette. Curves, Color Wheels and HSL Secondaries are all great tools to match shots and fix all kinds of issues in the image, so applying a creative look before these initial steps feels very illogical to me.

5) Make all tabs deactive by default when applying the effect. This would save time and increase performance. It's easier to activate tabs as you go than deactivating tabs you don't really need. Lumetri Color is a resource hog compared to obsolete color correction effets and I've notices that deactivating unused tabs makes a noticeable difference in performance.

6) This is also a personal preference, but please allow user to decide if Lumetri Color Panel should activate "Selection Follows Playhead" -setting or not. This is the biggest reason why I use Lumetri Color from Effect Controls Panel.