Frankly, I'd be terrified to ride with what amounts to a thermite charge strapped to my body, with a 'ripcord' to activate it in case of a crash...
But if you are ok with that, I think the greatest problem with backpack is, again, 'cantilever' and the fact that it puts all weight on your shoulders.
Splitting the pack in two and making it 'body hugging' and using a system of straps like a modern body armour that weights about as much (research it) and is supposed to be worn if not all day, than certainly for hours at a time should work. Using 3d printing and 3d scanning and some composites on top will help a lot and may even protect the battery and you in case of a crash - of course 'safety third' and all that, but I think there are easier and less painful options if you just want to kill yourself...