It looks simple to add a new flag in these cases, one that is ignored by LFS but should be output to InSim. It's easy for me to locate those cases where a modification or move is taking place (where it sends a delete immediately followed by add).
What exactly is it you would like? Something like PMO_MOVE_MODIFY (value 8) and that same flag would be placed in the delete packet and the add packet when they are being sent as a pair?
Is there any need to distinguish between (1) moving objects and (2) generally changing attributes like colour, size, etc? Or can they be treated all the same? There aren't all that many flags available in that byte so I only want to use up the minimum, but of course it should be as useful as possible.