Looks to me like you’re stuck between a rock and a PR nightmare. I’m guessing if you checked flow every minute (or 5 or 10 minutes) the meter battery life would be drastically shortened. I see an aftermarket wired back plate for the flowmeter on the horizon.
I never understood how you could power a transmitter and measure flow for such a long time with such little battery power…now I get it. I bet there were many internal meetings on this topic.