To say, I think this is not a good idea due to the fact that some songs just aren't meant to be nightcored... I like some nightcores, the techno ones which are actualy meant to be in a speedy tempo, but an auto-nightcore mode would make me be in even more pain... And I so hate backing beat, don't know how it got there but I swear there is nothing playing 1/1 all time in every song, and that is not in the handmade nightcore eighter...
This mode would truly be such a music-breaking soda. Please don't do this, I am hurt enough by coming to lobby and seeing everyone play vocaloid, bad apple and some other shit and popular songs with thousands of plays. I believe that osu!, even while being pink, is not a pig, so I beg for a miracle and reconsideration........
I wonder if anyone here cares...
EDIT: Sometime in the future:
A player comes in to play.
He checks every room available.
Everyone is playing Nightcore.
He makes a room and no one comes,
because it is not Nightcore.
How is that fair to people who hate it? And I actually believe this will happen to the most pro-players because most of them only cares about how hard the beatmap is, not about the song itself...