Hey guys, crazy stuff! I tested the shield without a LiPo battery and it still works perfectly! The LiPo battery charger simply acts as a 4.2V voltage regulator and the SIM7000 is perfectly content with that :)

I'm considering making a new version of the board that uses a voltage regulator that taps into the 5V from the Arduino instead of using the LiPo battery. Stay tuned for more updates!