This seems to work. Posting it in case someone else finds it helpful.

package MakeMethod;

use strict;
use base qw( Class::MethodMaker );

sub new_hash_init_required {
    my ($class, @args) = @_;
    my %methods;
    foreach (@args) {
        $methods{$_} = sub {
            my $class = shift;
            my $self  = ref($class) ? $class : bless {}, $class;
            my %args  = (scalar @_ == 1 and ref($_[0]) eq 'HASH') ? %{
+$_[0]} : @_;
            foreach (keys %args) {
                if (my $setter = $class->can(" __CMM__ $_")) {
                    $setter->($self, $args{$_});
                } else {
                    $self->$_($args{$_});
                }
            }
            die "must specify required" unless $self->can("required");
            my @req = $self->required;
            foreach my $req (@req) {
                die "$req does not exist" unless exists($self->{$req})
+;
            }
            $self;
        };
    }
    $class->install_methods(%methods);
}

sub required {
    my ($class, @req) = @_;
    my %methods;
    $methods{required} = sub { @req };
    $class->get_set(@req);
    $class->install_methods(%methods);

}

1;
[download]

While I had trouble grasping the C:MM docs, reading the source made it much clearer.