Who can answer your customers?
Messages from customers arrive in your company's customer inbox. The owner can always answer, and so can team members the owner has allowed to handle customers. Handling customers is a per-member setting — members don't get it automatically, and guests never see the customer inbox.
Replies go out as your business: the customer sees the company's name and logo, not which person replied, and the whole exchange stays in one continuous conversation however many people work on it.
The owner turns customer handling on or off for each member. Give it to the people who should speak for the company, and switch it off when that changes — no role change needed.
When someone is removed from the workspace, they lose the inbox along with everything else. There is no shared company login for anyone to keep.
The inbox itself gives the team tools for working together — assigning conversations, statuses, priorities, labels and internal notes.