I am sure if the devs put enough thought and time into Shujinko, he could be an outstanding character to play as. The way I see it, I think Shujinko should be a jack of all trades kind of character. He strength comes from the variety of fighting styles and powers he has and utilizes and not being an individual specialist in each. For example since he learnt and absorbed the powers from Sub Zero's ancestors he could be able to create a small ice ball and freeze individual opponents. But his ice summoning powers are much weaker than Sub Zeros, who can form ice spikes and a kori blade.
Thus I feel his moves should be a conjunction of the variety of powers he has got. For example he can have a parry move where his upper part of his hand gets frozen and the opponent freezes on contact. Shujinko then connects with a fiery blackflip kick. Thus it pays tribute to the original characters from whom he learnt these moves (scorpion and sub zero) but using them in his own improvised way. The enhanced version can follow with a teleport punch immediately after the back flip kick. Another move he could have is the whirlwind kick. Though originally Kung Lao's MKDA move, I think it will fit him best which can pay homage to two characters, Bo Rai Cho and Liu Kang (Whirlwind kick= flying kick + bicycle kick). The enhanced move could be a fiery version doing more damage.
Also he could have an anti air where he throws his kunai when the opponent is in the air and smashes them onto the ground.