And how is a sales rep (especially an independent one) going to keep profitability high? I can't imagine any pro salesperson who's been around the block in this industry would work on a percentage of profit if they're not also in control of production.
As far as I'm concerned, if I'm selling for you we can establish minimum pricing, and if I miss something and make a mistake - backcharge me. But if I did everything right and your crews can't get it together, or it snows in September, or you order the wrong materials? Not my problem. Pay me. I sold a $70k retaining wall job several years ago, and the company had so many staffing problems and other goofiness that it took them six months to finish the job. It was bad enough smoothing the customer over throughout it, I can't imagine if at the end I was told "hey, it wasn't profitable for us, your commission is now zero."