The interaction between the characters of both universes would be a big draw. How would the Doctor get along with Ruby and her team? And the exploration of new worlds and timelines together could be really exciting.
There could be fun crossovers of powers and abilities. Like Doctor Who's time-travel skills combined with RWBY's unique weapons and fighting styles.
One idea could be that Doctor Strange somehow gets transported to the RWBY universe. Maybe he's there to help deal with a powerful Grimm that has magic - like abilities that the normal Huntsmen and Huntresses can't handle. He could use his magic to teach the RWBY characters new ways of fighting and also learn a thing or two from them about their unique combat styles.
One interesting idea could be a crossover of different timelines within RWBY. For example, characters from the past meet the current ones and have to deal with the differences in their worlds. Another could be a crossover of different teams in unexpected ways, like Team RWBY having to team up with a rival team to face a common enemy that is more powerful than any they've faced before. And sometimes, there are crossovers that involve alternate versions of the characters, where their personalities or abilities are slightly different, which can lead to very unique and engaging storylines.
It could have exciting time-travel adventures combined with Sherlock's sharp detective skills. Maybe characters from both universes team up to solve complex mysteries across different eras.
One of the coolest elements is the clash of the two settings. RWBY has a world full of magic, like Dust, and unique kingdoms, while Dead Space is all about a desolate, horror - filled space environment. In a crossover fanfiction, seeing how these two settings blend is really engaging. Maybe there are parts of Dead Space's technology that are brought into the RWBY world, or vice versa. Also, the different character personalities from both universes interacting can lead to some really fun and unexpected moments.
The RWBY characters are used to a world full of Grimm and Huntsmen. When Doctor Strange arrives, his different style of magic and his more 'cosmic' view of things would be a shock. For example, he might use his magic to create portals, which could be used for both transportation and as a weapon. The RWBY team would have to adapt to this new form of combat. Doctor Strange, on the other hand, would have to understand the RWBY characters' reliance on Dust and their team - based combat. He might find their loyalty to each other and their cause quite inspiring and adjust his own actions accordingly.
There could be unique character interactions and unexpected plot twists. Maybe seeing Doctor Who characters in a completely different fictional universe brings fresh and exciting dynamics.
It could be the combination of different universes and characters. Maybe seeing how the Doctor interacts with characters from other shows in unexpected ways.
One interesting concept could be the Doctor meeting characters from other science - fiction universes. For example, if the Doctor were to cross over with the Star Trek universe, it would be fascinating to see how the Doctor's time - traveling and alien - facing skills would interact with the Star Trek crew's exploration and scientific knowledge.
One idea could be that Superman arrives in the RWBY world and has to learn about Dust and its powers. He could team up with Team RWBY to fight a common enemy, like a powerful Grimm that is immune to normal attacks but not to Superman's strength. Another idea is that Ruby discovers she has some Kryptonian-like abilities and Superman helps her understand and control them.
One idea could be the Doom Slayer arriving in the RWBY world. He could be on a mission to stop some sort of demonic invasion that has seeped into Remnant. His powerful arsenal and unwavering determination would be a huge contrast to the Huntsmen and Huntresses of RWBY.