I think they use him because hes the only human(looks mostly) that is part of zergs in the story of starcraft, so its best beginning character that fits for her corruption. You know innocent person that is slowly corrupted wont be like "yes i want to be gangbanged" , "yes ill fuck that dog/monster" right of the bat so i dont see any big problem. Using him as a opening "snack" of ch.3 is also fine but if they do like 50/50 scenes with him and zerg on ch.3 then yeee that will be annoying i think max 2 scenes they could add with him somewhere in the middle of ch.3 and end it with that and focus on all other characters.
Still the biggest issue is the time they need to make such small updates its just pictures afterall that you re-use and adjust alittle to fit scenes. that amount of "new art" is 1 month of work for diligently working artist.
same thing happens with witch hunter trainer , summertime saga and many others that i dont know.