I think it would be pretty cool if xur sold weapon engrams. I understand that most people believe that you can be punished with an exotic engram because of different classes, but a lot of people have 3 characters that are different classes. With 3 characters, getting an exotic not for the equipped class isn't that bad because you can transfer it via vault. Weapons would still be a problem because of duplicates and exotics you don't want, same with armor for me.