The projects that I shoot are quite "site specific". Face detection can provide fairly accurate detection that can help find an image. I will shoot a particular site several times a year. The faces in one site will not appear at a another.
The way that unknown faces are classified automatically shows that the pool of faces is all faces that have ever been recognised by Lightroom.
This doesn't match the workflow. For a given site, there is a closed subset of faces that it could be. Drawing from the universe of all faces doesn't make any sense.
So the suggestion is having user defined face collections where I can specify which group of faces should associated with a given folder. This means that a group of faces can be associated with several folders.
I also know if I'm working on a new project with faces that I've never photographed before. It would be useful to be able to flag this so names aren't associated automatically and incorrectly. You end up correcting names that are totally incorrect. "This folder should have no default faces". In this scenario, the grouping of like faces is super important (which LRC does a reasonable job at doing).
As a second point, when you do update / correct the names in the Similar List there's no recalculation step to check similarity again once you've made an update to the name label. I have multiple photos of the same person in separate contiguous sequences. When you select multiple and edit the name in one block, those update and are added to the confirmed list, however the obvious other blocks containing the same person don't have the updated (new) name suggested as a possibilty. Double clicking their name at the top and checking the confirmed list is one way around this. But you want a sense that what you just corrected has been intelligently applied and that an updated set of suggestions is now presented to you. Right now you have to still re-type the name again to correct the incorrect suggestion.