It seems to me like it makes more since to just make use of the things rails does automagically...

awesome_template.rb

class AwesomeTemplate < Template
  # We don't even care about custom behavior in this template. 
  # We just want to be able to identify it as a different type
end

cool_template.rb

class CoolTemplate < Template
  def some_method
    # special case for this particular type
  end

  def some_custom_method
    # no other template needs this method
  end
end

template.rb

class Template < ActiveRecord::Base
  # has some fields and stuff

  def some_method
    # handles default behavior
  end
end

With STI you would write a migration that adds a "type" fields to the templates table. Rails automatically sets the type to the subclass's name. BAM. You got types.

I'm going to flesh out both these examples more later...