the reason why they made this version unable to roll back is because the main intent of this release in the first place was to stop all 3rd party development. If they let users roll back then no-one would update and everyone would just keep 1.0.2. But sadly they are forcing people to keep 1.1.1 to stop 3rd party apps. Really sad actually, doesn't seem to make any sense why Apple would want to do this. They normally like to side with the innovators.
Of course you can go back by design. Every device I own you can install old firmware on. It's just firmware. Apple went out of their way to block you from going back not because of design but because they want to stop third party apps and unlocking.