I know its dumb... but if non custodial wallets are popular to onboard. Wouldnt a non custodial nostr service do it too? Just think if a service held relays, gave you your account using an email and can recover through it, also advertise who is posting and is popular on said service, and also provide services directly like translations and etc. Think the all in one service for nostr onboarding could help. 

 I think a big thing i missing here on this too is making it so when you follow someone it automatically will add relays that best provide that persons content.