Lite accounts are very important, with Leo twitter sign ups, this is already solved to some extent because you simply need to link twitter and you're a user in a snap.
It won't be ideal for lite accounts to be over some different account, it has to be the same, but integreted in a way that a user does not have to worry about keys. More educative contents are definitely needed, the RC request is also needed but for this there should be some form of verification(not personal information particularly), a way to prove not being a robot to avoid exploitation.
What do you think of Ceramic accounts? That is something SPK Network is building.
As you mention, a good solution may be that someone trustworthy can keep the newbies' keys until they are ready to join Hive fully. But of course, that would have risks.
I'm not exactly sure how the ceramic accounts work, do you have some resources I can explore for more clarity?