This is still my best guess for the biggest Deception in a game packed with Deception :

IE - Liu Kang's 2 known forms will be 2 of 3 outfits. LK will possibly be the playable sub-boss rumoured. When you play against him on VERY HARD and defeat him, the Zombie outline will fall/melt away OR the Ghost will drift upwards towards the heavens, revealing SHANG TSUNG!

Liu Kang has been Shang Tsung all along! Because LK's soul was so strong and so pure, Shang was unable to morph completely, hence the Zombie/Ghostly appearance that resulted.

Back to the game and once revealled if you can beat Shang Tsung on VERY HARD then a brilliant cut-scene showing Shang being banished to hell and Liu Kang's spirit reforming into flesh and Blood will eventuate! Now Liu Kang will have a 3rd alternate outfit for future use, his Resurrected Human form!

I'd go further to say that beat Shang Tsung on VERY HARD at the first attempt and he too will become unlocked for future use.

Ok all of this is speculation on my part but the whole Liu Kang really being Shang Tsung makes so much sense and really could be the major Deception of this game.

Shang has extensive morphing abilities and took Kangs soul afterall.