Hehe - regarding the bathroom topic: here in Germany we have a farmer who makes a lot of livestreams from his work and when he "has to go" he says "I have to check the tire pressure....." - this became a really funny running gag when he got a Claas chopper with tracks...
I've been watching since the beginning. It's hard to fathom how far you and Grant have come in the last few years.
Doesn't the oil and dust associated with harvesting create a sort of grinding paste on the combine chains?
For short range radio communications between the grain cart and combine, you could use a pair of inexpensive FRS (Family Radio Service) radios as alternatives to your commercial radios. They are not very expensive but FRS will work across the field for you.
The bathroom question is funny. My two sons and I spent many years hiking/backpacking together. One evening we were trying to convince my wife that she needed to go backpacking with us. She said she only camped where there was a bathroom. My youngest son, probably 14 at the time, commented "Mom, the world is your bathroom". She still hasn't gone backpacking. LOL.