When placing the beetle, can he be placed on top of another piece as long as he doesn't touch an opponent's piece? The rules don't appear to prohibit this.
You can't. It has to be placed like all other pieces:
NB When it is first placed, the Beetle is placed in the same way as all the other pieces. It cannot be placed directly on top of the hive, even though it can move there later.
From the bottom of page 5.