Having a dead body on your settlement is a bit annoying. Especially if you moved it and upon getting back to your setlment you find out its back to the same spot.

Therefore, can Dev include a body decaying option or a clean up option to permanently remove any dead body after 24h, no matter if on a setlment or not ?

Bet you are talking about the dead body at the bridge at Sanctuary, I've got a dead wild dog there too and that one can not even be moved.

Use the console:

markfordelete

Note: This command will delete the object from the game permanently. Make sure you select the correct target and that it isn't an unique object. You might have to reload the area to get the object to delete (fast travel somewhere else and back).