We have backpack equipped config, backpack entity config, but not backpack BLOCK config.
It'd be nice to have one. Features I'd like to see in one include:

1. Being able to set the backpack block as blast-proof/fire-proof or not
2. Being able to set how it is equipped (whether by shift-breaking, shift-right-clicking, etc.)
3. Being able to set whether it's affected by gravity or not.
4. Could move the "machine interaction" part to this config section too, as it deals with the backpack "block".