First sign up with email and pass, google, facebook signup .... later they can "claim" their account and keys .... meanwhile keep some notification that the account is not claimed.
Agreed on retention, one of the main thing shoul be try to provide support/votes for newbies.
We currently do that with Vimm. I suppose it would be up to the front end if they want to support that. Remember, hive.blog is only supposed to be an entry point for the blockchain. It wasn't meant to be the main front end. Anyone who develops an app/website on the Hive Blockchain can handle their onboarding however they want. I would imagine simplified onboarding on PeakD would theoretically be possible, if the developers made it a priority.
-@ddrfr33k