4. Encapsulation is advisory; subclasses require no implementation knowledge of the superclass.

Actually, that's easy. Just use package variables instead of lexical variables.

package My::Class;
use Scalar::Util qw( refaddr );

# package hash for inside-out properties, instead of lexical
our %name;

sub new {
  my $class = shift;
  bless {}, $class;
}

sub name {
  my $self = shift;
  if (@_) { $name{ refaddr $self } = shift }
  return $name{ refaddr $self };
}
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I did a variation on that for my highly experimental Object::LocalVars and called it "outside-in".

Actually, while I haven't tested it, there's probably no reason it couldn't be done today with thread safety and all the rest with Class::InsideOut -- it only needs a hash and it doesn't check to see if it's a package hash or a lexical hash. You'll get thread safety, Storable support, etc.

Equivalent to the example above, but robust:

package My::Class;
use Class::InsideOut qw( public register );

public name => our %name;

sub new {
  my $class = shift;
  register( bless( {}, $class ) );
}
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P.S. I did a quick test changing a test-suite property to our instead of my and the test suite ran fine, so I suspect the outside-in variation works fine with Class::InsideOut.