To validate that you have a whole team, track the team membership each iteration, beginning with the first iteration, and review it regularly. Confirm that the whole team starts together and finishes together. Yes, this may seem like a relatively simple (or even simplistic) thing to track, but if the goal is to have stable, dedicated teams, then having an indicator immediately available to confirm that this happens can be a big incentive to actually having stable, dedicated teams—especially if you need to convince others in the organization that problems with team stability are real.
As another simple metric, make a rough estimate for the time required to coordinate information across the team at the beginning of a release. Find a mechanism to share the same truth with the entire team. Use a dashboard, a common whiteboard, a wiki, an information radiator, or whatever works. Use that mechanism as a way to share information during the daily standup. Re-evaluate the time required to coordinate information across the team at the end of the several iterations. Compare the results. If significant progress was not made, or rather the time required for coordination did not decrease, try a new mechanism.