Custom / External sensors Arduplane

I want to install Pixhawk on an manned ultralight aircraft only to log data… as a flight data analyzer…(NOT AN AUTOPILOT)
1- I may need to install an external temperature and barometer sensor. I found some documentation about connecting MS5611 directly to Arducopter… Is this option available in Arduplane mode as well or not? How? Clearly My altitude estimation should use external sensor data instead…

(One more thing… If I want to use Pixhawk Cube, does it measure the outside air temperature or the internal (Temperature controlled) section temperature?

2- I want to a read and log some load-cell values as well… They may be Analog or SPI data… Can I just simply connect them to ADC GPIOs and read them back on QGC? How can I do some calculation with them in the Code? in PX4 I was planing to use simulink embedded coder for PX4 … but I guess there is not a similar tool for arduplane. So I should manually change the firmware code… Is there a documentation about how can I access the ADC or I2C or SPI custom sensors values, process them and send them along other data to ground station mavlink messages and I get those values in SD Log file and also Mission planner screen.

Please help me in this relatively new topic for me