I think what you want (and more) can be done without any change to the software.

All you need to do is define a membership type which is used exclusively for new members and specify this as the "Given on registration" membership.  Within that membership type you can define exactly what they can read or do.

For example (see attachment), I have defined a membership type called "Awaiting Approval", and I have set that as the "Given on registration" membership.  Like that I am able to fully configure what they can do or not do when their profile is new.

 

There's a section in the "Admin" manual about creating membership types.

I've changed my membership types to how I want them.

All my memberships are currently free.

Try looking carefully at the bottom of all of my many posts 

Moved this topic to "Ideas Exchange"