Improve Queue Callback to work with smaller number of waiting callers

Currently, the Queue Call back feature does not work well for queues with small numbers of waiting callers (< 5).

For small queues, but with long queue times such as a support queue, or accounts queue, where the number of callers waiting may only be a small number but where the duration of the call may take a while and has a limited number of available agents, providing a way for users to select a callback, even if they are the only person waiting in the queue, is helpful to the caller as they do not have to wait on hold.

I would propose enhancing the user experience by including a time factor in the queue call back as an option.

For example, if a queue has a single caller in a queue, and if the anticipated hold time exceeds a user-defined value, then offer a call back. Do not however call the user back if there is only 1 agent in the queue, until the agent is off the phone. If a new agent logs in then before they can take a call from the queue, the call back would be executed first.

This is most helpful for queues where limited experienced agents are available, and resolution times may exceed that of which a caller is willing to wait.