If Shang Tsung did return, i'd be more concerned with how the button inputs, for him to morph, would clash with the combos (i know they got away with this in early MK's). Would be better if he naturally shape shifted from fighter to fighter, in the same way Chameleon switches colours. He could even morph in to characters no one has seen before, which wouldn't be playable. These would be the souls he took. I think all of this would be an effort in 2.5D though.
Bring back grandpa MK1 Shang Tsung.
I, on the other hand, would like him to morph into toher characters. I think this is a very unique ability of his, and while MK:DA/MK:D(Konquest)/MK:A he had his own skills without morphing, I always miss.
Soul steal and morphing. This shouldn't be ruled out of him. Oh, and fire skulls.
Look, now Baraka has grown hair and beard! Shit, the time does fly...
I've been a sucker for Shang Tsung from the first time I've seen him in MK back in the '90s and would most definitely want him to return, but as of the WB era, he's been nothing but a clown (in an MK9 finisher, a real one at that). He's everyone's bitch, everybody mocks him, knocks him down, his power is lower than in all previous MKs. Makes you wonder whatever happened to the imposing, regal attire-garbed warlock from MKA's intro who kicked Shao Kahn's and Liu Kang's ass and all but made it to the top of Argus's pyramid? If NRS is to get him back, I want nothing less than the independent Shang from MKDA-MKA. That said, he could again likely turn up as someone's stooge - either Kronika's or Kotal Kahn's - since the "boss villains" have already taken their positions.