I used WhatsApp until it was acquired by Facebook. Since then WhatsApp has become even more dominant (in South America WhatsApp is so dominant that users do not know how to use native SMS).

Can android support containerized apps of chrooted apps such that OS calls are routed to the host system _unless_ that call is overloaded. Suppose contact-list calls are overloaded and direct the app to a subset of the contact list (only the set that the user wants to share with the app).