I have a disc audax bike planned, and I'm going to use a 1" steerer for that bike. My rationale is that braking loads on that bike will not be too severe. I think that if I was going to do touring on it, I would want a 1 1/8" steerer. I thought about this for quite a while and then found that Crust bikes has a 1" steerer disc fork, so I figured if they were still in business, people weren't dying because of it. I can understand why a builder wouldn't want to do this though.

Putting discs on a road bike is a pain. They aren't made with space for a disc. If you really want this, it's probably best to get new bikes.