As Lew indicated, we've been down this road before. I've never known of a building department that's required a 3D view of the plumbing as it relates to the fixtures in 3D. All they require, and it's usually only the Commercial applications, is an isometric that indicates sizing. It doesn't have to be to scale, it doesn't have to slope, it doesn't have to be in color...... Just some lines with size indicator loops - simple CAD. I've been doing these things for almost 50 years, and I've never had a plan checker tell me that I didn't show the correct slope, or how much oakum and lead needed to be in the bell and spigot cast iron joints - yes, I was 14 years old, crawling under houses with a ladle full of molten lead to pour into a cast joint and then have to cork it, and come back for more lead. In fact, I still have all of my old tools (pot, ladle, corking irons, & ropes, and even a few boxes of oakum).
Anyway, my feeling is that if you do a fancy 3D plumbing system drawing, and the plumber does it that way, guess who is responsible if it isn't right (venting, sizing, wet vents, slope, etc.). Just lines with sizes, based on the code, done.