I played with this some time ago. I believe you are way over thinking it, but the issue is the user's $_SESSION. You will find that a page reload may be required to get the cookie on the browser to sync with the site.
In any case, I believe all requests are sanitized already via the modRequest class.
Just capture the content in a form and send it to a page with the correct Snippet in it, but be very careful. Shaun has gone to lengths to make sure your site isn't compromised through the login script, and there are some very helpful functions in his Package to help protect you from abuse.
var form=$('#registerform').serializeJSON();
You are switching the form to JSON. Does his Package even support JSON as a valid input or is it looking for a PHP Array? Do you to need to do a fromJSON in a Catcher Snippet to hand off to his Register Snippet?