Well, perhaps in the 'rwby meets god fanfic', the god has come to Remnant (the RWBY world) because there is some sort of imbalance or threat that only the RWBY team can help with. So the god decides to guide them, and along the way, the RWBY characters learn about the true nature of their world and their destinies. They might have to make some difficult choices as the god presents them with different paths.
In the 'rwby meets god fanfic', it may start with a strange and otherworldly event that leads the RWBY characters to encounter the god. The god could be a benevolent one, wanting to help them reach their full potential. For example, Ruby could be given a special task by the god related to her silver eyes. Weiss might learn a new form of Glyph magic from the god. Blake and Yang could also be given unique opportunities to grow stronger and face their inner demons. This encounter with the god could change the whole course of their adventures and how they interact with the world around them.
In a 'rwby meets god fanfic', Ruby, Weiss, Blake and Yang are the most likely main characters as they are the focus of the RWBY franchise. But depending on the direction of the fanfic, other characters like Penny or Jaune could also be important. Maybe Penny has some connection to the god due to her robotic nature, or Jaune could be the one who accidentally stumbles upon the god's arrival and then informs the RWBY team. Still, the RWBY girls will probably be the ones with the most significant interactions with the god.
One possible plot could be that Ulquiorra, with his cold and emotionless nature, is suddenly thrust into the world of RWBY. He might initially be confused by the colorful and energetic world filled with Huntsmen and Huntresses. Maybe he gets involved in a battle against the Grimm and his unique Hollow powers create a stir among the RWBY characters.
Well, it could be about the characters from Kingdom Hearts ending up in the RWBY world. Maybe Sora and his friends join forces with Ruby and her team to fight a new kind of Heartless that are somehow related to the Grimm. They'd have to learn to use each other's abilities and work together to save both their worlds.
One possible plot is that a powerful and evil force is trying to take over both the RWBY universe and the Red vs Blue universe. The characters from both sides are thrown into a new world created by this force. They have to find a way to escape and stop this evil. Along the way, there would be lots of funny moments as they misunderstand each other's cultures and ways of fighting. Ruby could be fascinated by the Red vs Blue's use of guns, while the Red vs Blue guys might be shocked by the Grimm. They would gradually learn to cooperate and use their combined strengths to defeat the bad guy.
The plot could involve a common enemy that threatens both the RWBY world and Konoha. So, the characters from RWBY and the ninjas of Konoha have to team up. For example, Salem's forces could somehow cross over into the Naruto world. The ninjas would be amazed by the unique abilities of the RWBY characters like semblances. In turn, the RWBY team could learn about chakra and ninjutsu. This would lead to some interesting training sessions and battles where they combine their powers in creative ways.
One idea could be that the RWBY characters are transported into the Overwatch universe and have to team up with the Overwatch heroes to fight a new common enemy, like a powerful omnic - Grimm hybrid. Another could be a friendly competition between the two groups in a series of combat trials to see who is more skilled.
One idea could be that Goku accidentally travels to the RWBY universe during a sparring session that goes wrong with Whis. He could be mistaken for a powerful Grimm at first, causing chaos. Then, he teams up with Team RWBY to fight a new super - strong Grimm that threatens all of Remnant.
One possible plot could be that Naruto is somehow sent back in time and meets his mother Kushina. He gets to know her as a person, not just as the mother he never really knew. They could train together, and Kushina could share some of her unique Uzumaki clan techniques with Naruto.
Well, it could be that Harry and Logan meet in a magical forest. Harry, being from his wizarding world, is intrigued by Logan's mutant abilities. Maybe they start by being cautious of each other, but then they realize they can help each other in some way, like Logan protecting Harry from some dark wizards who are after him for his magic, and Harry using his magic to heal Logan's wounds that won't heal on their own.
Well, the plot could involve Naruto and Meliodas teaming up to fight a common enemy. Maybe an evil force that threatens both their worlds. Naruto's ninja skills and Meliodas' demon powers would make for an epic combination in battles.