alt Hacker NewsVery interesting project.
From a product uptake perspective, I could suggest that since a user is still building trust when they begin use - to only require as few permissions as needed. I'd punt that profile update requirement out personally for another method later.
An example might be when a user has used your app for N sessions, or after N months.
They should prompt the user for permission when they use a feature that requires it, explain why, and allow them to cancel if desired. Have seen this pattern used many times elsewhere.