What I read from your initial post is, that you want to organize your photos along the following lines:
Root folder
- Customer A
- Session
- Imported
- MySelection
- CurrentCustomizing
- ForFinalSelection
- AcceptedByCustomer
- Customer B
- …
Capture One is probably the app that works with sessions most easily. There is no need to invest into C1 though. If you create the necessary folders in advance, you can shift images between folders from within PhotoLab Library view. One problem remains: PhotoLab stubbornly redraws new images - instead of providing a possibility to quickly cull with the built-in previews.
Vote here: