I think Harry would also clone Dumbledore. Dumbledore was one of the most powerful wizards. His wisdom and ability to see the bigger picture would be invaluable in the clone army. The clones could guide others and make important decisions, just like the real Dumbledore did.
Another likely candidate could be Sirius Black. He was a brave and loyal friend to Harry. His skills in combat and his ability to think on his feet would make the clones of him great fighters. Also, his loyalty would ensure that the clones would be dedicated to the cause Harry is fighting for in the fanfiction.
Definitely Hermione. Her intelligence and vast knowledge of magic would be a great asset if cloned. She could help solve complex magical problems and come up with strategies in battles.
He could have found a magical artifact. There are many artifacts in the Harry Potter world that have strange and powerful abilities. It could be that this artifact has the power to create clones. He figures out how to use it, perhaps with the help of Hermione who is good at researching such things. And then he starts creating his clone army.
In the 'Harry Potter makes a clone army fanfiction', perhaps Harry creates the clone army to protect Hogwarts. He might use some ancient magic spells he discovers in the library. These clones could be modeled after the greatest wizards in history, like Merlin. They would bring a whole new level of defense to the school against the dark forces.
It could also change his relationships. His friends might be worried about this new and rather extreme power he has. They might question his motives and whether this is the right way to deal with the problems in the wizarding world. On the other hand, his enemies would definitely be more cautious around him.
The originality of the story. Harry Potter has a unique plot that follows Harry's growth and his battle against Voldemort. This is not a recycled or cloned idea.
I think Dumbledore might be a candidate in the fanfiction. He's the most powerful wizard of his time and could offer Harry deep insights into magic, history, and the fight against the dark side. Also, Luna Lovegood could be a tutor in her own strange but brilliant way. She has an unconventional view of magic that might open new perspectives for Harry. Then there's Sirius Black. He could teach Harry about the wizarding world outside of Hogwarts and some spells and tricks he learned during his time as a fugitive.
Well, a big theme is the exploration of different cultures. The wizarding world in Harry Potter has its own unique culture, and so does the galaxy in Clone Wars. Fanfictions may show how characters from one world react to the customs and values of the other. Also, the idea of good vs evil is a common thread. The fight against Voldemort in Harry Potter and the struggle between the Jedi and Sith in Clone Wars can be combined in interesting ways in these fanfictions. For example, the Death Eaters could be compared to the Sith in terms of their goals and methods.
Hermione Granger might also be a key character. She could be involved in researching the theory behind the shadow clones and helping Harry control or improve this new form of magic.
Maybe Harry Potter could be magically transported to the Star Wars universe and become a Clone Trooper. He might use his magic skills to help the Clone Troopers in their battles, like using spells to deflect blaster fire or heal wounded troopers.
Some popular Harry Potter clone fanfiction include 'The Lost Years of Harry Potter'. This one fills in the gaps during the summers and other unaccounted - for times in Harry's life. It gives a lot of character development and backstory. 'The Gryffindor Princess' is another good one, which focuses on a female character who becomes a central figure in Gryffindor house. She has her own set of adventures and relationships within the Hogwarts environment. 'The Forbidden Forest Secrets' is also worth reading as it uncovers many mysteries and hidden things in the Forbidden Forest that were only hinted at in the original books.
One main theme is the clash and combination of different cultures. The military discipline and technology - based world of the Clone Commander meets the magic - filled and somewhat archaic world of Harry Potter. Another theme is often friendship. As the Clone Commander interacts with the characters in the Harry Potter universe, they form bonds and friendships.