As a professional Hat Block maker, I also endorse this even if it means some may not order wood blocks.
It does give milliners the skills to at least create unique blocks that they can test and then send to us to be made in wood. In fact, it is a must that you present your block maker with a model to follow.
You mentioned how helpful it is if we have a concept for a new block to make it out of the foam first rather than sending you pages of sketches and measurements. Once we have it as we want it then send to you to customise as a wooden one. Discussing with Graham about a little block I need soon we have decided to knock it up in foam & test drive it for the hat & if it works will send you the foam knock up. I know you are up to any Challenge -E :)
schematics are a different language to many, and even well done drawings and sketches are too easy to misunderstand by both parties. On the other hand, when provided a half decent model, I have seldom got it wrong