Is there a way for me to usefully use the "run-on" time configured for each HVAC in Cortex?

Let me explain..
I have 3 HVAC zones (1 per floor). Each HVAC has it's own temperature input and separate zone valve object (relay) connected to physical zone valves that control the circulating flow to the rads on that zone.

As I understand the Run-on, once the HVAC determines that the set-point has been reached, it keeps the demand output 'on' for a further time, as set in the "Run on time".

During this "Run on time" what I'd like to do is throw open the other zone valves, so that the 'spare' heat in the circulating water can benefit the whole house. For example, in the middle of the night, my ground floor zone is set really low till about 5am. But the bedroom zone keeps the bedrooms topped up @ 16C during the night so turns on a couple of times for approx 30 minutes. During the "run on" time from the bedroom zone I'd like to "take the chill" off the ground floor. That way there is a little less heating required there come 5am...

To me (maybe I'm wrong) this seems a good way to use the latent heat in the system rather than just let it ebb away in the pipes & floor voids (no matter how well lagged). Especially seeing as during this run-on time, the boiler is still getting a normal "demand for heat".

I guess what I'd need is some way to get a signal from the HVAC object when it's on Run-On mode. I could then connect this signal to the other HVAC Zone's zone valve objects (output relays). But I dont see such an output.....

.... Is anyone doing anything similar?
.... Or have any suggests?
.... Or maybe I'm suffering Sunday madness?