Such a high count of probe points is almost begging for a 3D-scanner like setup. With cameras and flashlights you can produce a cloud of millions of probe points in no time...then filter out the polygone-planes that are equal to the neighbours to compress the file.
Some smartphones can do that too. Maybe add a phone gimbal to the printer and let the smartphone scan the bed...
@dc42 Agree and in any sequence it should work like that, but in case a single G30 command is entered in console I think it's better if the probe type is reverted to P9 (basically this is the only reason I made it in a way that it defaults back to original behavior).