This module should have the functionality to create and manage Online Appointment Schedule as well like https://calendly.com/.
The appointment scheduling functionality should have a public interface for taking a available time slot for the meeting similar to the Calnedly.com. Dolibarr internal user will share the public interface link with the intended Third-party via email; similarly how it is done win Calendly. For every internal user the link should have different user_ids, because same public interface will be used for scheduling meeting for all internal users.
After enabling the module, there should be an Availability settings similar to the Calendly. So internal user can easily setup their available time slot.