Can .700 be used with the Fcc modification?
Probably the simplest way is to change your country setting to United States and keep your device in airplane mode.
There are several YouTube videos that are pretty simple and walk you through steps to modify the Mavic. Many of them involve rolling back the firmware to .700 and below to get these mods to work. They are not hacks, but back doors left opened by DJI. Those doors are being locked with the latest firmware.
Search for Simi Travels on Youtube to see one of several solutions for FCC mode.