I say just keep them the way they are, they already have a taper to them, and the raw denim is what it was made to be and to fit the customer, otherwise you should of bought a different model if you wanted more of a taper.
I think your mistaken. Dukes dont have a taper at all. They are straight leg fit.
I believe they are all button fly. I personally like button fly, at first I didn't like it but I got used to it. The only thing that sucks is when you're in a rush to zip up your pants, it takes a little longer than just zipping it up.
I actually find buttons faster since my buttons holes are all loosened up, i can just pull and they all come off.