Automatic scene detect and effect instancing.
For using Lumetri to grade existing videos, scene detect as in other grading apps would be a huge time saver.
As would the ability to apply instances of the color grade to similar shots. They can be pasted clones of the effect with a chain icon to represent the link. Adjustments to the grade will effect all the copies of it applied in the edit. Clicking the chain icon will un-instance the effect for the selected clip.
Ryan Creighton commented
Yes please! Everything should be instance-able. Effects should be like MovieClip instances in Flash/Animate. Create one, name it, and apply it in different areas of your movie. Select one, modify it, and all instances update to reflect the change. This would save me literally hours.