The multitasking feature of multiwindow in touchwiz allows for true multitasking. Paranoid Android has done a pretty great job of multitasking with features like halo which also includes a version of multiwindow. Halo allows you to move your apps around the screen. Now this feature of Paranoid Android is available to you without the need of running a full fledged rom. In fact all you need is to be rooted and to have the xposed framework installed to your device. The Xposed Module "Flying Android" by developer "tkgktyk" allows for multitasking by allowing you to move apps in the form of windows on your homescreen. You can also move things around like specific UI elements. The recent apps, and status bar can all be moved around the screen. This also will allow for easier one handed use as you can easily move apps to places on your screen for easier reach. Grab this module at the link below.
Via XDA