If actually doing it I would be inclined to set up the transmit end to be powered ahead of the enlarger timer
No need. Takes just a few milliseconds for a uC to power up, send its signal and if so desired even engage in a little confirm-and-repeat. I know, because my darkroom lighting setup relies on such technology. So does virtually every modern remote controlled lighting appliance. Delays are a non-issue with this kind of technology.