Listen’s 1×1 widget is as simple as a 1×1 widget that shows the book cover of the currently playing audio book, overlaid with a play button when not playing. That’s it. It simple, yet it allows you to start playback from a widget small enough to fit in with other icons.
I don’t know why this widget size isn’t standard for other media players, but it should be. You might argue that music players need more advanced playback controls than just play/pause, but with pretty much every music player having playback controls in the notification pull-down these days, that’s not really an issue either.
So, if any Android media player developers are reading this, please look at Listen and follows its example.