Here is a rough idea for multitasking when you alt+tab. It's like a deck of cards; as you tab, the card on the right slides into the centre, and the previous card shuffles itself underneath the others on the left. Ideally, it loops (just an opinion!), and is scrollable.
As you can see, I wasn't particularly inventive with the open apps, but it is showing 5 windows of the Files app, and in this mode, the corresponding app icon lights up on the dock to signify which app is showing, a la elementary.
It's all quite self-explanatory really, but if you have any questions, fire away. I also added my own cursor idea in there just for fun. Let me know what you think guys!