I have been thinking about this specifically. Have you tried out my invite cards? Currently they land the user logged in on peakd.com, but I could A/B test the cards taking different routes. I have been thinking exactly as you said, if the invite flow directs them through creating their profile and an introduceyourself post. We can empirically test the effectiveness in retention.
RE: The Single Most Impactful Thing You Can Do For Hive: Upvote a Newbie