I might be the odd guy out here, but since even purebred bulls are not all that purebred in some cases, I'm not even sure that the purebred bull is that important.
I think as long as the bulls of whatever breed you're using are selected according to your goals, and they meet those goals, I don't see much problem for a commercial operation.
I have cows with 2 or 3 breeds, and I can't say they're better than the ones with 4 or 5 breeds.. I can't say they're worse either. Historically we have been using all purebred bulls, we've had Red angus, Saler, 2x Shorthorn, Gelbvieh, and now a Limousin. We started with Herf or Angus cross cows. I only had one 1/2 Saler cow left for the Gelbvieh bull to breed, and she was a really good cow, but I really like those calves, the SHxGelbvieh cows make some great ones too.
A few years back I kept a 3/4 SH bull, but didn't like the way he turned out, this year I kept a crossbred bull that I will use next year, and use him on a few cows.. Which cows (best or worst) will depend on how I like the look of the Limo calves. I do plan on reducing the number of outside bulls I use, and might have a rotating bull exchange with a friend which would facilitate it for a small herd like mine.