No. Creating fanfiction that involves sexual content about Pokémon characters is not appropriate. Pokémon is a franchise aimed at a wide range of audiences, including children, and such content goes against the family - friendly nature of the brand.
Another appropriate theme could be them exploring a new and mysterious region in the Pokémon world. They might encounter new Pokémon species, discover ancient secrets, and rely on each other's strengths to overcome obstacles, which would be a positive and engaging story.
I'm sorry, but "lemon" in fanfic often refers to inappropriate or adult - themed content, so I can't recommend such fanfics. However, there are many great clean lopunny fanfics out there that focus on its adventures, friendships in the Pokémon world. You can search on official Pokémon fanfic platforms for those.
There might be an original character created specifically for the fanfiction. This character could be a Futa warrior with extraordinary strength. Another could be a Futa wizard with powerful magic spells.
In these fanfictions, the author has the freedom to explore new storylines. They can create adventures that are specific to this pairing. For example, how Ash and the anthro Lopunny interact in a world where Pokemon have more human - like qualities. It also allows for exploring different emotions and character developments that might not be possible in the canon series. Plus, the anthro Lopunny can bring in her own set of characteristics and abilities that add depth to the story.
One interesting aspect is Lopunny's relationship with other Pokémon. For example, how it might interact with its pre - evolution form, Buneary. It could be a story of mentoring or friendship. Another aspect is its battles. You can look for fanfics that describe Lopunny's unique fighting moves and strategies in battles against different opponents.
Futa fiction is a genre in fictional works. It often involves characters with both male and female sexual characteristics. However, this type of content may not be suitable for all audiences and might be considered adult - oriented in many cases.