In general, the greater the complexity - the greater chance for errors. When working with significant forces as described above, set-up errors can cause a rope to snap or send an attachment like a carabineer or pulley flying like a bullet. Getting hit by a snapped line or carabineer can cause serious injury. You really need to evaluate the strength of your rope and anchors to ensure nothing can break.
The Z Drag isn't something we practice very much so it can take some time to figure out. It also takes time to locate and set-up suitable anchors for this system. Add additional time for safety dampers and brakes and 20 - 30 minutes can go by very quickly. Compare this to simpler methods like the Armstrong method, vector pull, and simple turning - all of which are safer and much faster.
For these reasons, avoid heavy mechanical advantage systems when rescuing a pinned boater. Often time is of the essence for a trapped paddler. If possible, extract the boater and deal with boat recovery when everyone has had a chance to rest.