Another interesting plot could be that a powerful villain has created a device that is merging the Naruto world and the DC world together in a chaotic way. Naruto and Big Barda have to find a way to stop this while also dealing with the strange new hybrids of their respective worlds that are being created as a result of the merge. This would involve a lot of exploration of both worlds and their unique elements.
One plot idea could be that Naruto somehow gets transported to the DC Universe where he meets Big Barda. They team up to fight a common enemy that is causing chaos in both their worlds.
Maybe Big Barda visits the Naruto universe. She could learn about chakra and ninjutsu while Naruto learns about her technology and fighting style. They could then exchange skills and use them against an approaching threat. In this type of plot, there would be a lot of cultural exchange between the two very different universes.