This is a common scenario that I've seen addressed by a number of users in the following manner:
- Build your customer support interface (CSI) (i.e. the side used by your customer support reps) using Direct Line
- Your bot pipes through the all the user messages to the CSI which stores all the conversations. Reps can see a list of all the users interacting with the bot and the history of each of those conversations.
- When escalation to a human is needed, the bot flags one of the conversations needing attention
- Your bot then brokers conversations between the accounts (i.e. Facebook End User <-> Your Bot <-> CSI). Essentially the customer support rep is creating a response, which is being posted by the bot back to the end user
This means there's no need to add an additional person to the conversation. (Facebook currently only allow 1-on-1 conversations with bots).