Fighter's Guild skill. Crossbows won't ever be a weapon. I highly doubt we'll ever get ANY new weapons anyway. Giving us the Warden Class was a fluke cause they already had it more or less complete since Beta.
There's quite a really nice looking dwemer ballista (nonfunctional) around Summerset that I very much checked for an E prompt so I could try to siege passers-bye
I wish. Just fighters guild though..... They actually acknowledged people talking about spears and crossbows a while back, but said they can't promise anything.