Naruto is sure to be a central figure. Then there could be a new character, a half - demon who acts as a bridge between the ninja world and the demon army. Hinata might also be involved, perhaps using her Byakugan to discover secrets about the demon army. And of course, Kakashi could be there to guide Naruto and the others in dealing with this new threat.
Well, it could be about Naruto forming an alliance with a demon army. Maybe they come together to fight a common, greater evil that threatens the ninja world. The demons might have unique powers that Naruto and his friends need to learn to use effectively in battle.
Obviously, Naruto is one of the main characters. He is the central figure from the Naruto universe. And then there would be characters from the orc army. There might be an orc chieftain who leads the orc army and interacts with Naruto, whether as an ally or an antagonist at times.
Most likely Naruto would be one of the main characters since it's in the Naruto universe and the title seems to imply a focus on a single character's story, which in this case is probably Naruto.
Since it's a fanfiction, the main characters could be any two characters from the Naruto series. It might be Naruto and Sasuke, as they are very popular characters and their relationship has a lot of potential for such a story. They could put aside their differences and form an army together.
Obviously Naruto himself would be a main character as the source of the clones. Maybe Sasuke could also be involved, either as an ally or an antagonist in relation to the clone army.
Most likely Naruto would be one of the main characters, since it's a Naruto - related fanfiction. There might also be his friends like Sasuke or Sakura who could be part of this army of glass concept.
It could be a mad scientist - type ninja who creates the droid army. This ninja might be someone who was shunned by the ninja community for his unorthodox ideas about mixing technology and ninjutsu, and now wants revenge by using the droid army to take over.
It could be Orochimaru. He's always been into strange experiments. He might create a robot army to get revenge on the village or to prove his superiority.
Sasuke could be one of the main characters. He might initially be skeptical about Naruto's plan to rebuild Revan's army but later come around and offer his skills. Another could be Kakashi. His experience and wisdom would be valuable in guiding the new recruits. Sakura too, with her medical skills, could play an important role in taking care of the army members during battles and training.
Well, obviously Naruto's friends like Sasuke, Sakura, and Shikamaru could be part of the army. Sasuke with his powerful Sharingan and combat skills, Sakura with her medical ninjutsu and newfound strength, and Shikamaru with his strategic mind. Also, ninja from other villages like Gaara from the Sand Village, who has his own unique abilities and a bond with Naruto, would likely be in the army.