In your AssemblyInfo.cs remove this:

#if DEBUG
[assembly: Application(Debuggable=true)]
#else
[assembly: Application(Debuggable = false)]
#endif

Then add it to your MainApplication like this:

#if DEBUG
[Application(Debuggable = true)]
#else
[Application(Debuggable = false)]
#endif
   public class MainApplication : global::Android.App.Application
   {      
      public MainApplication(IntPtr handle, JniHandleOwnership transer): base(handle, 
        transer)
      {
      }

      public override void OnCreate()
      {
        base.OnCreate();
        CrossCurrentActivity.Current.Init(this);

        //A great place to initialize Xamarin.Insights and Dependency Services! Add 
         some function that you want.
      }

   }

And ideas on how I can refactor the Android Project to begin with a MainApplication instead of MainActivity?

According to the link that you provided, if you want to Android project start with MainApplication, you just create new class name MainApplication.cs in Android project, if you want to perform some functions when Android project starts, you just add some code that you want in OnCreate() method.

#if DEBUG
[Application(Debuggable = true)]
#else
[Application(Debuggable = false)]
#endif
public class MainApplication : global::Android.App.Application
{      
    public MainApplication(IntPtr handle, JniHandleOwnership transer): base(handle, transer)
    {
    }
    public override void OnCreate()
    {
        base.OnCreate();
        CrossCurrentActivity.Current.Init(this);

        //A great place to initialize Xamarin.Insights and Dependency Services! Add some function that you want.
    }

}

You can see when you run project,enter MainApplication firstly, then Mainactivity,I think the article that you provided, has solved your question.

I am working on a Xamarin.Forms application that has Xamarin.Android and Xamarin.ios projects. I need to use the CurrentActivityPlugin for Android.

I need to perform some functionality when the Android app starts, hence I want to my app to begin with a MainApplicaiton instead of a MainActivity as shown in the docs here.

And ideas on how I can refactor the Android Project to begin with a MainApplication instead of MainActivity?