Wow...creating and then editing offset planes seems to be harder than it should be when dealing with non-planar BRep bodies.
My suggestion: When one says "create an offset plane" and clicks on a non-planar BRep face, do some averaging or some other magic to create a plane that is at a "similar" angle to the face...or maybe along the averaged normals of that face within a set distance/diameter or something. Right now, I can't even click on the face at all.
I see you have dynamically updating planes from the "plane along path" command...it would be awesome to click-drag my mouse along a BRep face and see a constantly tilting offset plane changing around, and then allow me to settle on one I like.
Thanks!