At the conference, external speakers should present on specific topics.
If there are already several external AppSec consulting companies under contract to the hosting company, the consultants involved in existing projects are perfect candidates to present to the conference. They can use their own examples and stories, and it is easier to present internal materials if all participants are signed-up to the same NDA (Non-Disclosure Agreement).
Never underestimate the power of team collaboration, or of team members getting to know each other. Social events are important, and the model of the OWASP Summit is also a good example of a conference for security champions, as is the Microsoft Blue Hat security conference.
(from SecDevOps Risk Workflow book, please provide feedback as an GitHub issue)