Tbh I'm a bit at a loss as to why a difficulty level has to be made unlockable?
If DDD is starting a trend here it's not a particularily well thought out trend, it reminds me of the non-stackable difficulty trophies of Re: CoM, forcing one to do six playthroughs. <__<
PPPPPSSSSSSSSSSSHHHHHT, WE DON'T MENTION THIS EVER AGAIN. I dare them to do this in any other game.