Hi tikiss and all,
very good work, I'm interested in one maybe two machine-populated units.
Just some notes:

1. ATM 4 GPIO left unused. If GPS reset is not used and 3Dfix led can be sacrificed, we could have 6 gpios to let the unit control focuser stepper motors using already available Radeck Astroberry Focuser indi driver. On the power shield side, only a JST like connector to link one of those mini stepper controller modules is needed.
2. MCP3202 can be replaced with 3208, and populating 1 INA328 and OP-AMP per channel we'll have amps readings per-device instead of total. Maybe it's an overikill, don't know.
3. the OneWire pin can be used to chain one or two DS18B20 temperature sensors to monitor stuff that has to be kept dew-free: since ambient temperature and relative humidity are already avavilable, we can calculate dew point temperature and automatically regulate heaters at minimum power needed to keep dew away. Obviously lacking (or not working) the sensor, the channel works in manual power mode. I've already done it with Arduino, code is simple and I can contribute it.