The issue is the entrance into split-view, which should expose the springboard, not the dock.

The intuitive way to launch a second app would be to slide in from the right or left with two (three?) fingers, which would expose a compressed view of the springboard in split view. Then you could access all the apps intuitively (by swiping to the next page of apps) and launch the second app in the intuitive click-an-app method. This could even be tiled in a golden-rectangle geometry to expose a third app.

All you're trying to do is repurpose the slide-right slide-left function to expose springboard in a new way, which can be done with a multi-finger gesture.