MIT App Inventor 2 is a compiler intended for educational / training purposes
Several commercial spin offs are Thunkable, Appy Builder and MakeRoid; there may be more...just search for them..
You asked "Are there any other AI2 variations that allow user defined package names?" App Inventor users probably do not know. Why not try the other versions and let us know Martyn? This is the MIT App Inventor 2 forum.
Your app created in AI2 crashes when uploaded to AppyBuilder. As the characteristics of these clones diverge from the original App Inventor base, this is to be expected. You can adjust your code or ask for advice on the AppyBuilder forum to make your aia compatible if you are not happy with this educational compiler.
Consider graduating to App Inventor (the free Java based professional compiler). You can make the package name anything you want there. Another free professional compiler is Delphi Community Edition; it uses object Pascal to develop.. A relatively inexpensive Android/ios compiler is Basic4A (B4A) ...thereis a version that compiles both Android and ios.
Manually renaming packages works. Laborious? You want to experience laborious? Use Android Studio. Also, you will be able to build more elaborate apps.
Let us know what you discover.
Regards,
Steve