Cascading is possible within the mixer families, not between. The AI mixers additionally have the option to add a stagebox. The stageboxes aka RM rack mixers can also be cascaded via AVB I (master & slave).
If I may give you an advice: Do not waste your time and money on "old" technology. At some point you might reach a stop of functionality. If you have some old equipment and create the "environment" it needs, it's all fine, at least as long as things work. Why not look for one of the Series III mixers? They're much more fun and you can buy them second hand already for a good price... ;-)