Half of jQuery Serialize is param(), so half of something that deserializes a query string is going to be a deparam. Unfortunately I haven't been able to find a good standalone deparam. For now I recommend getting the jQuery BBQ library and using that. If you don't need the other stuff you can remove them. I read somewhere that Ben Alman (cowboy) planned to extract deparam into its own module.

For the rest of deserializing, you'll just need to loop through the object that deparam returns and for each key and value pair in the object, select the form element based on the key, and set the form elements value to the value.