As a result from that SO question. One repeating pattern in form creation is
$fieldset->addField, so that presented itself as a key way to
grep in files.
user@magento:~/www/app$ grep -rin "addField.*text" * | grep -i product
code/core/Mage/Adminhtml/Block/Catalog/Product/Edit/Tab/Super/Config/Simple.php:140: $fieldset->addField('simple_product_inventory_qty', 'text', array(
There were about a dozen results which were quickly narrowed down (we're not caring about giftcard or Attribute sets). I'm not 100% sure THIS file is the answer but it seems that some logic could be added to catch whether or not the input's
name=="Name" and then a maxlength could then be added in.