A crossover could involve the characters swapping abilities. Imagine Tracer from Overwatch having the ability to call in a Titan like in Titanfall 2. Or a Titanfall 2 pilot having the ability to use some of the support abilities of the Overwatch heroes, like Mercy's healing. This would create really interesting and unique combinations in combat scenarios.
The plot could center around a new threat that only the combined forces of Titanfall 2 and Overwatch can defeat. For instance, a powerful alien race that has the ability to disrupt technology, which affects both the high - tech Titans and the various advanced weapons and gadgets in the Overwatch universe. So, heroes from both sides must put aside their differences and fight together.
A really interesting storyline could be centered around the conflict between the two factions in Titanfall and how the Overwatch heroes get involved. Maybe the Omnics from Overwatch are somehow related to the IMC or the Militia in Titanfall. This would lead to a complex web of relationships and battles. The Overwatch heroes would have to adapt to the Titanfall combat style, and the Titan pilots would learn to work with these new, diverse heroes.
Pharah and a Titanfall scientist. Pharah is a highly trained soldier with a focus on aerial combat. A Titanfall scientist might be researching new ways to improve Titan mobility or weaponry. Their alliance could be born out of a need to create some new kind of weapon or technology. The scientist could use Pharah's combat knowledge to better understand how their creations will be used in actual battles, and Pharah could get access to some really advanced tech.
One great Overwatch Bastion crossover fanfiction is 'Bastion in Another World'. It has Bastion being transported to a fantasy realm. The author does an amazing job of describing how Bastion's mechanical nature interacts with the magic of the new world.
Well, a significant theme is the exploration of morality. In crossover fanfictions, Zenyatta often encounters situations where the moral boundaries are not as clear - cut as in his Overwatch world. For instance, in a crossover with a post - apocalyptic world, he has to decide whether certain actions that seem immoral in his world are acceptable in the new context for the greater good. Another theme is the power of his oracles. When he crosses over, his oracles may function differently, and this exploration of his powers in new settings is also a common theme.
There's a fanfic where Genji from Overwatch gets transported to the Naruto universe. In this story, Genji has to adapt to the ninja way of life. He learns about chakra and how to use it, while also teaching the Naruto characters some of his own skills. It's really interesting to see how the two different power systems interact.
One great Overwatch Reaper crossover fanfiction is 'Reaper in Another World'. It combines the dark and brooding nature of Reaper with a new, fantastical setting. The author does a great job of keeping Reaper's character intact while exploring new storylines.
You can try looking on fanfiction websites like Archive of Our Own (AO3). It has a large collection of crossover fanfictions. Just search for 'Overwatch Young Hanzo' in the search bar and you'll likely find many interesting stories.
Character interactions play a huge role. For instance, seeing how Mercy from Overwatch would react to the more brutal and often evil characters from Doom. And also, the plot usually revolves around some sort of threat that forces the two universes to collide. It could be a Doom invasion into the Overwatch world or a common enemy that requires both sides to team up. The different cultures within the two universes are also important. Overwatch has its own set of values and teamwork dynamics, while Doom has a more survival - of - the - fittest kind of feel. This contrast can create interesting storylines and character development.