apart from the graphics limitations in terms of colour on the ST(not STE) and cheap ST sound rendering, it would have been possible.
maybe the main constraint would have been the same as for the amiga, ie the 11 disks. it could be the fact that fewer ST owners had an HD that pushed Lucasarts not to release an ST version.
DO NOT FORGET THAT ST WAS ALMOST DEAD BACK IN THAT TIME (TURNING POINT BETWEEN ST&AMIGA WAS 88 I GUESS)
..JUST WANT TO POINT OUT ONCE AGAIN THIS GREAT WAR BETWEEN ST AND AMIGA OWNERS BACK THEN!!!