It would be very cool if we could do more with Kaede during the night sequence and maybe outside of that to. A long with Syn & some of the others like the Mad scientist or the Nun one day.
Syn will stay unfuckable iirc, but there was recently a poll regarding which enemy do we want to fuck next - unholy nun has won
So the next fuckable enemy (just like sexy psycho) will line the nun, but I have no information on when will that be
As for other characters, I'm sure they will eventually be added