Magento Onepage Success Conversion Tracking Design Pattern - magento

Question

My intent is to track conversions through multiple channels by inserting third party javascript (for example google analytics, optimizely, pricegrabber etc.) into the footer of onepage success .
I've accomplished this by adding a block to the footer reference inside of the checkout success node within local.xml and everything works appropriately.
My questions are more about efficiency and extensibility.
It occurred to me that it would be better to combine all of the blocks into a single block reference and then use a various methods acting on a single call to the various related models to provide the data needed for insertion into the javascript for each of the conversion tracking scripts.
Some examples of the common data that conversion tracking may rely on(pseudo):
Order ID , Order Total, Order.LineItem.Name(foreach) and so on
Currently for each of the scripts I've made a call to the appropriate model passing the customers last order id as the load value and the calling a get() assigning the return value to a variable and then iterating through the data to match the values with the expectations of the given third party service.
All of the data should be pulled once when checkout is complete
each third party services may expect different data in different formats
Here is an example of one of the conversion tracking template files which loads at the footer of checkout success.
$order = Mage::getModel('sales/order')->loadByIncrementId(Mage::getSingleton('checkout/session')->getLastRealOrderId());
$amount = number_format($order->getGrandTotal(),2);
$customer = Mage::helper('customer')->getCustomer()->getData();
?>
<script type="text/javascript">
popup_email = '<?php echo($customer['email']);?>';
popup_order_number = '<?php echo $this->getOrderId() ?>';
</script>
<!-- PriceGrabber Merchant Evaluation Code -->
<script type="text/javascript" charset="UTF-8" src="https://www.pricegrabber.com/rating_merchrevpopjs.php?retid=<something>"></script>
<noscript><a href="http://www.pricegrabber.com/rating_merchrev.php?retid=<something>" target=_blank>
<img src="https://images.pricegrabber.com/images/mr_noprize.jpg" border="0" width="272" height="238" alt="Merchant Evaluation"></a></noscript>
<!-- End PriceGrabber Code -->
Having just a single piece of code like this is not that big of a deal, but we are doing similar things with a number of different third party services.
Pricegrabber is one of the simpler examples.
A more sophisticated tracking service expects a comma separated list of all of the product names, ids, prices, categories , order id etc.
I would like to make it all more manageable so my idea to do the following:
combine all of the template files into a single file
Develop a helper class or library to deliver the data to the conversion template
Goals Include
Extensibility
Minimal Model Calls
Minimal Method Calls
The Questions
1. Is a Mage helper the best route to take?
2. Is there any design pattern you may recommend for the "helper" class?
3. Why would this the design pattern you've chosen be best for this instance?

Answer 1

You could create a custom module that extend Google Analytics
In /app/code/local/MageIgniter/SiteTracker/etc/config.xml
<config>
<modules>
<MageIgniter_SiteTracker>
<version>0.1.0</version>
</MageIgniter_SiteTracker>
</modules>
<global>
<blocks>
<googleanalytics>
<rewrite>
<ga>MageIgniter_SiteTracker_Block_CustomTracking</ga>
</rewrite>
</googleanalytics>
</blocks>
</global>
</config>
Then modify this method as needed from see app/code/core/Mage/GoogleAnalytics/Block/Ga.php
In /app/code/local/MageIgniter/SiteTracker/Block/CustomTracking.php
class MageIgniter_SiteTracker_Block_CustomTracking extends Mage_GoogleAnalytics_Block_Ga
{
protected function _getOrdersTrackingCode(){
....
}
}

Answer 2

sounds like a lot of fun by getting to know Magento I'd suggest you to start from Alan Storm's blog and magento knowledge base
The reality is that you don't need another pattern on top of already designed framework and easiest way and maintainable way is to follow existing patterns and in your case it would be:
make your extension
make your templates by service provider
make your layout descriptors by provider
tie them together with one block or use multiple blocks (to be more manageable)
no matter what you do the most gain in performance in case of Magento comes from caching your block output and layout descriptors and handlers are cached by default for you
so think through what you can cache
* css, js can be minified and compressed
* templates that you need most probably contain new information cause each order is different so you can't cache those and you need new data to send to service provider
if you don't add new business logic then i'd suggest to code your output methods in blocks as most of the time you are just filling javascript variables with data here and don't need to calculate anything new