Does anyone know of a way to change the Ellipsoid pre flight?
Currently the P4P RTK is locked into WGS84. At our mine we use NAD83. I have a verticle offset of 153.894 ft which seems to work well when using ground control points to verify, but from what I have read, the verticle offset will start to vary more and more over large surveys and large elevation changes. Being an open pit mine, we have both. I know DJI had said in their initial release you would be able to select desired elipsoid, though this doesn't seem the case.
Perhaps in a firmware update coming soon, or if anyone has a workflow they would like to share reading and editing the exif data to calculate the correct ellipsoid for all geotags.
Thanks.

NAD83 is not an ellipsoid, it is a datum. NAD83 is based on the GRS80 ellipsoid (WGS84 is both an ellispoid and a datum; the WGS84 datum is based on the ellipsoid of the same name).

Images collected with WGS84 geotags can be processed to create output products in your favorite flavor of NAD83 and coordinate system of choice in most photogrammetry software.

Not sure what vertical offset you are speaking of- is that the Geoid height for conversion from HAE to NAVD88 orthometric? If so, you just use the value appropriate for the ellipsoid you are starting from (WGS84). The Geoid height varies over space, but this is true regardless of the reference ellispoid.