BLF for queue


we have the problem (small company) that our (one) support agent works on calls in a queue.

When he knows the current call will last longer than a few minutes, it would be best to pickup calls in the queue and offering them a callback instead of waiting forever.

But he does not know if someone is in the queue when he is on the phone.
It seems to be not possible to have a red BLF button when someone is in the queue.

Is it possible to incorporate the following asterisk patch into freepbx?

Thank you!