This afternoon I spent some playing with a jQuery Form Validation plugin to determine if it will help me resolve the issue with required fields. The initial results look fairly promising as I was able to tag a couple fields on a test form and they were flagged when I submitted it.
In the image above, the jQuery Validation plugin added the “Thus field is required” when I submitted the form with those fields empty. This is exactly the behavior I want, the challenge now is to scale my Proof of Concept (PoC) to work in the generic case of the plugin. The Google form defines a block for each input field and the class the denotes a field as required is assigned to one of the DIV blocks that wraps the label and form element (e.g. INPUT or TEXTAREA tag) as opposed to the form element tag itself. This makes finding the required elements a little tricky.
The real challenge I think will be input groups (e.g. radio buttons and check boxes). I need to do some jQuery research before I have a solution but assuming I can figure out which elements to select, I believe this will solve the problem with required fields.