First, Happy new year to ya hope you have a wonderful year as for the devlog, I love how your mind works, I like that you stick to the mechanics of WCA S1 but also introduce a new one as well. Sides, a single route to each girl will be a little bit of a stretch for you but it'll be worth it in the long run. As for the DLC/side characters, I dunno about this one but you can make a poll about it.
And as for "CERROS" (LOVELY very LOVELY by the way) there are only 3 questions I'll ask about her,
1. will she be relevant to the main story?
2. what are her personalities/behaviors, is she going to be a likeable character?
3. and If 1 and 2 checks out where would you want to put her/introduce her?
If these 3 checks out then she'll be good addition to the WCA universe if not, you can either trash her out (Which I really don't want to recommend since she has a great concept design) or introduce her at a later chapters where she would be relevant to the main story or just ADD her as a DLC character.