Forward calls from Call Queue to Ring Group when agents logged out

We are a veterinary practice and have Call Center with Call Queues set up, and our agents consist of our receptionist(s) sitting at our reception desk. When the receptionists are on-duty, we don't want calls going anywhere else in the office unless the receptionist transfers calls.  The Queues are set up to go to voicemail if the caller "escapes" with the * key. This works exactly as we want.

However, there are times when they are both unavailable for a portion of the day (breaks and lunches, for example). During that time, we want callers to flow through the call queue, but with if no agents are logged in, we want the calls to ring to a Ring Group instead of directly to voicemail.  The Ring Group are physical phones in our treatment area, where medical staff know they are covering lunches and will answer the phones. 

The Call Queues do have an option to 'reject' callers from the call queue if no agent is logged in, but that just routes them down the 'escape' path, which goes to voicemail.

Does anyone know of any way to set up a dial plan to do what we need? i.e. when agents are logged in, callers sit in queue or escape to voicemail, but if no agents logged in, bypasses call queue and goes to a Ring Group. 

Alternate would be if there was a way for a receptionist, who is a supervisor but not an admin, to switch dial plans if they are leaving on break.  From what I've seen, someone would need to login as an admin to switch dial plans, but even that's not straightforward. And often someone with the admin credentials just isn't there or available to switch the call plan. Some thoughts I had, but I can't figure out if any of this is possible:

• A node in the dial plan that conditionally routes calls depending on whether agents are logged in or not. I don't see any nodes that can do this.
• A * code, perhaps even with a password (although not necessary) that would switch dial plans to an alternate "lunch dial plan". Can't find anything about this being possible.
• A * code to switch schedules, which would then be tied to the "lunch dial plan", and then another * code to switch back.
• An API call that would switch dial plans - I could set up an applet on our intranet site, that when triggered manually by receptionist, would trigger a webhook with an API payload to switch dial plan. Can't find reference to this in API guide.
• Lastly, could the receptionist stay logged in, but forward their phone to a dial group?  If this worked, problem would be that since the agent phone is forwarding calls as they happen, the ring group could get bombarded with calls.  But that's better than nothing.

Any other thoughts would be appreciated!