I believe used homebuilt planes now out number ones still owned by the builder. They are already part of the aviation economy as is.
Pro type of builds happen all the time now. I know of two relatively local shops that do it. Have been for 20 years. The only change would be not having to look the other way, which is hard for rule enforcers to do, or or should it be OR, now they would have a shop they can oversee with new regulations. For people who don’t know, the GA inspectors get payed on how many certificate oversights they have assigned. More is better. The airline inspectors get payed on how big the airline is.
Rarely does the FAA go backwards. Doubt they would here. Not with MAX hanging over their head. Just like basic med. Looks like a savior, but the fine print really not, if you do what they really want you to do. It’s kind of like the homebuilt rules now, don’t really self disclose if there is real problems, but just sign the papers.