As I suspected - there aren't any answers to my question.
I'll answer my question myself with a workaround, then, and wait for someone else to come up or for the creators of Unity to provide us with the same functionality under Android as under iOS.
To achieve the desired effect, I decided to only have 1 activity and multiple fragments. The activity extends UnityPlayerActivity meaning that when it loads, that takes the time Unity needs to load. Then, when navigating throughout the app, I only swap fragments containing entire screens and make use of the UnityPlayer.pause() and UnityPlayer.resume() methods, as well as the setVisibility method to make it go away.
Hope that helps if anyone has any similar issues.