Nekoishi, you have to take into account that Nights as a game-mode is not something many players will have known about coming into this, so it's alien to them... and sure, this is SS7, the 'last' special stage of the game... but even still.
It can't be made super hard or your average player, even with practice, may never get all 7 emeralds, then you have people banging on the forum doors for 2.0 style special stages back or something so they can get all 7, SS8 is the stage designed with Nights enthusiasts who want to be tested to play, SS7 has to be designed for people who's only experience with Nights is the first six special stages, which, isn't a lot.
And about the time losing thing. I find it perfectly fair that you can still manage an A rank even with a few hits, RAINBOW A is for perfectionists, A's are meant to be tough to earn, but not near-impossible, there are emblems for them after all, and im sure many people would just give up on the game-mode if they needed to meet rainbow A standards constantly.