Couldn’t you set the locks to fail closed? Then the reed switch just turns the circuit and the reader. I might be missing something though. And of course you’d need a backup for something like that.
Yes there are many ways to achieve extended battery life when you can control every aspect of how the reader works but in the case of a black box where you only have control over power and output, an IR proximity detector or PIR circuit is a simple, effective option.
My thought was just a switch inside the door handle. Pull the handle, the circuit wakes up for a minute or two.
We use a microchip capacitive touch sensor at work with a pad 8mm diameter and a conductive foam pad on top I can getread ranges of 20mm (through my desk)