The best way to improve the ability of the Scrum Teams in a Nexus to produce an Increment for the next Sprint is to reduce the amount of work that the teams pull into the Sprint. This will allow the teams to focus on delivering a high-quality and valuable product Increment that meets the Definition of Done and the Product Goal. Reducing the amount of work also reduces the complexity and dependencies among the teams, which makes integration easier and faster.

The other options are not advisable for the following reasons:

Asking the Nexus Integration Team to extend the Sprint to allow more time for integration is not consistent with the Scrum principles and values. The Sprint length should be fixed and consistent throughout the product development, and it should be less than a month. Extending the Sprint would compromise the feedback loop, the transparency, and the adaptability of the Nexus 11.

Reducing the number of Scrum Teams to reduce complexity is not a viable solution, as it would also reduce the capacity and the productivity of the Nexus. The number of Scrum Teams in a Nexus should be based on the size and the scope of the product, and it should not exceed nine teams 11. Reducing the number of teams would also disrupt the existing team dynamics and collaboration.

Adding another Scrum Team to the Nexus to increase capacity is not a good idea, as it would increase the complexity and the dependencies among the teams. Adding another team would also require more coordination and communication, which would consume more time and resources. Moreover, adding another team would not necessarily increase the value or the quality of the product Increment 22.