I just realized while building refining the powersupply circuit that having the batteries connected to the load at all times would be a bad idea and to solve it I would need another relay on the PSU-board. But my Attiny84 is out of I/O-pins.

The solution I came up with is combining the homeswitch with the radio triggerpin, since the homeswitch in any case will only be used when reconnecting the line and be unused 99.999999999% of the time.

This will require some minor modifications to the CPUboard.... or major, I will figure this out later.