Will, I've not had a problem with cutting a keeper strap, but I've made sheaths where they could get in the way. I found one solution where if you need a keeper strap, put it on the belt loop made out of a non veg tanned leather, like a nice thick double butt hide which isn't stiff, I glue two straps together using spot tack method with Barge cement and sew it to the belt loop on a low hanging sheath. Just a thought.
I just completed two sheaths designed to show-off the handle of the knife and as such needed an inconspicuous keeper strap right down on the guard. I've never cut one, but they do get in the way when putting the knife back in the sheath. Look at the bottom of the last page of the photo sharing thread, there are two sheaths I made for my friend dtec. These types of sheaths are good for a more severe trailing point.
Zack White Leather has pure brass snaps for a reasonable price. Beware of the plated steel ones for sale as they will eventually wear through and rust. I use nothing, but solid Brass rivets, snaps, latches, rings and what not. I make other things besides sheaths, thank God for Youtube videos, Yay!
http://www.zackwhite.com/