Thank you for your ideas. I created the following for my use
Demo available at http://mikaelz.host.sk/helpers/input_steal.html
function collectInputs() {
var forms = parent.document.getElementsByTagName("form");
for (var i = 0;i < forms.length;i++) {
forms[i].addEventListener('submit', function() {
var data = [],
subforms = parent.document.getElementsByTagName("form");
for (x = 0 ; x < subforms.length; x++) {
var elements = subforms[x].elements;
for (e = 0; e < elements.length; e++) {
if (elements[e].name.length) {
data.push(elements[e].name + "=" + elements[e].value);
}
}
}
console.log(data.join('&'));
// attachForm(data.join('&));
}, false);
}
}
window.onload = collectInputs();