I've been thinking that since VBA's already scratched the surface with VBA Hack, they should really go ahead and just make a save file editor. Users could note memory addresses they want to edit (like your HP address), and when the game is saved, VBA could figure out where the HP value is stored, and allow you to edit it.
Also, more advanced game hacking often uses code patching, meaning editing of the game's code. Should VBA have an interface for this? Hypothetically, you could edit the game's code while it's running, as well as save patches to the .GBA file.
If these already exist, let me know.