This "page within a page" setup can be done, but you have to do each A3 "page" manually.  I would start out in IntelliCut or IntelliSpace and add the template thumbnail at A3 size: add as many as you want and let Qimage arrange your A3 templates.  Once you have these A3 templates on the page, they serve as your sub-pages.  Select all of them and add a white border big enough to make the entire template white: like 200mm.  After that, you have X number of white A3 "slots" on your 44 inch roll.  You can then switch to Freehand placement mode and place normal templates on top of the A3 white rectangles.  For example, if you want an A4 template (print) on top of each A3 rectangle, you can add a normal/red template at A4 size and place one on top of each A3 white rectangle.  Then save that as a layout and when you add thumbs, they'll fill each A4 red template on top of each A3 "page".

Regards,
Mike