Seems like I can't edit my post, so...
I finally managed to get the form to submit (not sure what I did wrong in the first place) like I wanted it to inside the div-element. However, I'm getting these errors now:
useless setTimeout call (missing quotes around argument?)
_clearJSFFormParameters is not defined
A4J is not defined
[Break on this error] A4J.AJAX.Submit("j_id_jsp_129948...?javax.portlet.faces.DirectLink=true"});
it will be better to use RichFaces from the beggining in order to load content. you could use simpleTogglePanel with ajax mode or just use conditional rendering with rendered attribute for the div which should be hidden/loaded.
Thanks for the help. I'm still trying to figure this out. Anyway, simpleTogglePanel won't let me load a new page in a (div) element, right? I guess I would have to put (hidden) forms between the simpleTogglePanel-tags!?
I'd prefer to, dynamically, load the form in a prototype-new Ajax.Request-manner.