Hi help_3452, there seems to be several ways going about what you need, which makes it hard for me to tell you what to do. So I will make a few suggestions based on what I understand:
-I would still consider trying to use just the plain WWW::Mechanize for 'collecting the data'.
-I have bypassed java script before with that module. I would also suggest getting the 'Live HTTP Headers' module for firefox. This will help you bypass some of the java script by seeing the HTTP GET/POSTS that may be occurring as you navigate the site.
- I think you're making this harder than it may need to be by allowing the user to select the particulars of the forms. If this feature is a 'must have' to you, I would get the form names, and allow the user to select which forms they intend to 'submit', have them enter the required input and pass that to the submit_form method that mechanize has. Each input could be a 'field' within the 'form', maybe.. Here is an example of what I used to login with Mechanize::Firefox:

$mech->form_name('loginform');
$mech->field('email' => 'me@awesome.com');
$mech->field('password' => 'l337');
$mech->click_button(name => 'login');
[download]

The WWW::Mechanize module is basically the same in this regard. For each of those methods I just used firebug to inspect each HTML element and then coded it into the script.