Since the MC will obtain new skills or use new type of potions as the game progresses and this skills/potions are tied to acquisition through advancing specific character routes, in most cases I think some characters will have their routes blocked behind other character's progressions.
Since my idea is to try to make the story have coherence between girl routes, I don't want for example to make it so for example if the mc get's his ability to control the size of his dong with character "X", I don't want to then make a scene for a different character were the MC makes it smaller/bigger if you haven't already gotten the skill.