Deere did come out with shared coverage mapping this Spring. To utilize it you need to purchase machine sync activation for each display, and a Machine Communication Radio for each machine, and have updated everything to the 15-1 software. Right now Deere has a $1000 dollar discount on each radio which end June 1. We ran this on two planter tractors this Spring that both planters were in the same field and it worked good. One thing with the MCR solution is you couldnt go do all the headlands ahead of the other tractor they have to be synced first before the other machine could leave.

Dont know if this will help you for what you need but it is something Deere has availble.

Check it out on YouTube : https://www.youtube.com/watch?v=9Kt6Pxd0N_8