You cannot design the XML in the MAIN DOM at runtime. However, you might be able to pull this off in a secondary DOM. Even though there is a schema associated with the secondary dom, InfoPath doesn't hold you to it at runtime. So you might be able to pull that off.
HOWEVER!! In order to design the view to display those dynamic tables, you need to have some design-time structure available to bind your controls to. Thus it doesn't really matter what you might do in the background, you have to have some kind of a structure any way (in advance) in order to show those tables.
Your best bet is to develop a workable XML structure that will allow you to "look like" you are being all dynamic about things.