One possible plot could be that Lucy trains intensively with Natsu by her side for support. They might go on special quests to find magical items or training methods that can enhance Lucy's power. For example, they could search for an ancient spell book that has the power to unlock new celestial spirit powers for Lucy.
The main characters are clearly Natsu and Lucy. Natsu, with his fiery and impulsive nature, is likely to be there to encourage and sometimes push Lucy in her journey to get stronger. His dragon slayer magic might also play a role in training her or protecting her during dangerous situations.
She might use her celestial spirits in unexpected ways against the guild. For example, she could have her spirits create illusions to embarrass the members.
There could be her family members. Her mother might be the one constantly checking on her temperature and making sure she is comfortable.
One possible motive could be revenge. Another character might have a grudge against Lucy for something she did in the fictional world, like betraying a group or stealing something precious.
Well, there are several potential plots for this kind of fanfiction. Maybe Natsu is in an environment where he is constantly bullied and abused, like in a guild where some members are jealous of his power. Lucy, who has a kind heart, decides to take him under her wing. She might teach him self - defense or help him build his self - esteem. Another plot could involve Natsu being abused due to a family secret or a prophecy that makes others target him. Lucy, with her intelligence and courage, tries to rewrite the fate that seems to doom Natsu to abuse. This could involve going on quests to find artifacts or information that can change the situation.
Makarov could be her mentor. He is the master of the Fairy Tail guild and has a vast amount of magical knowledge and experience. He could guide Lucy in exploring deeper aspects of her celestial spirit magic, teaching her how to better communicate with her spirits on a more profound level, which would in turn make her stronger when summoning and using their powers.
One common theme could be family. Since it involves 'baby Lucy', it might explore how Natsu and Lucy build a family together. Another theme could be adventure in a new way, like how they protect their baby during their adventures.
One possible plot could be that the Howler is a warning about a dangerous magical experiment Hermione is about to undertake. It scolds her for not considering the potential consequences and warns her to stop. This would put Hermione in a difficult position as she has to decide whether to heed the warning or continue with her pursuit of knowledge.
One possible plot could be that Clary gets drunk and ends up confessing her hidden feelings to someone she has a crush on.
Well, first of all, Lucy can try to have an open and honest conversation with Lisanna. By expressing her feelings and asking Lisanna why she is acting this way, she might be able to resolve the conflict. If that doesn't work, she can choose to rise above it. She can pour her energy into her magic training, become stronger, and show that she is not going to be brought down by Lisanna's actions. She can also look for new friendships outside of the group that may give her more positive energy and support. Another option is for Lucy to take a break from the situation. She can go on a solo adventure, clear her head, and come back with a new perspective on how to deal with Lisanna.