tho seems to me it wouldnt be challenging what so ever if you would have 100 lives to beat 6 "super expert" SP levels as imo 3% i a ton imo.
Well, if anyone wants to do a test run go for it :P However, I am not sure how much lower then 3% you can go. Right now the 30th most difficulty level has 0.52% win rate. You would want the pool to be more then 150 levels or whatever it is if you do 1%.
Anyway, part of the fun is that some hard levels you could beat in few tries. However, then you could hit a run-killing level that takes all your attempts. Hopefully, if something like this is implemented, it also creates a proper incentive to make hard levels. Right now, the normal/easy levels get's all/most of the plays.
Also, just playing the newest SP level does get a bit dull after a while. So making it a challenge makes it more fun. Might even be a good way to hand out some points for playing community levels so those guys are not stuck at sub level 10.