Restructuring - app dev vs support

I've recently been tasked with thinking about how to restructure our department following the addition of two new managers in between our line managers and the head of department. These positions are Application Delivery Manager and Project DeliveryManager. Project DM is responsible for all new projects, Application DM is responsible for 2nd level support as we have a Tech & Ops dept that handle first level. Question is, currently employees under line management are informally undertaking support currently. Would it be best to split them into two, or use a matrix system?