looks a bit meh. And custom right unary operators are on the way out, so one can't even create one for this use case.
Anyway, for fun:
create function deref_jsonb(jsonb) returns text as $$ begin return $1#>>'{}'; end $$ language plpgsql;
CREATE OPERATOR # ( leftarg = jsonb, function = deref_jsonb );
select '"sdfasdf"'::jsonb #;
select jsonb_col['a']# FROM somewhere;
Anyway, for fun:
:)