You could try:

use Perl::Critic::Command ;

use strict ;
use warnings ;

{ package Perl::Critic::Command ;

  sub _render_policy_docs {
      my (%opts) = @_;
      my $pattern = delete $opts{-doc};

      require Perl::Critic;
      my $critic = Perl::Critic->new(%opts);
      _set_up_pager($critic->config()->pager());

      require Perl::Critic::PolicyFactory;
      my @site_policies  = Perl::Critic::PolicyFactory->site_policy_na
+mes();
      my @matching_policies  = grep { $_ =~ m/$pattern/ixms } @site_po
+licies;

      exec 'annopod', $matching_policies[0] or die "exec annopod faile
+d: $!\n";
  } ;
} ;

unshift @ARGV, '--doc';
Perl::Critic::Command->run();
[download]

which does pretty much what you wanted to do by overriding a method -- but by redefining the subroutine...

With use warnings you'll see it warn you about the redefinition. Of course, if the author changes the _render_policy_docs subroutine you're in a different sort of trouble... so: use at your own risk !