Would be helpful to be able to add insert effects that just affect the signal chain of the monitored signal. Say a performer wants some extra processing on their vocal for monitoring, like a more aggressive compression or a wetter reverb. You can add that just to the monitoring inserts without affecting the actual mix you have going. I think something similar can be accomplished with cue mixes, but there's something nice able not having to fiddle with sends.
This is very similar to the hardware monitoring blue-Z mode where you can place inserts ahead of normal inserts that are just used for monitoring. Also similar to the UAD console workflow.