Security Model Using Invoker's Rights

Oracle RDBMS 12.2.0.1.0

We are starting a new development project and perhaps now is the time for a security model change.  Development came to me for a READ account and a WRITE account.  Access to the database is through PL/SQL Packages.  That's a little unclear, so was thinking about adding something to their request.

DATA OWNER, CODE OWNER:   PERMIT

PERMIT will own the objects and create its procedures with authid current_user to use Invoker's rights.

PERMIT grants execute to PERMIT READ and the required SELECT privs on objects

PERMIT grants execute to PERMIT_WRITE and the required S,I,U,D privs on objects