The problem as I see it, is being able to remove them if they are a single unit with a snug fit. With individual chocks placed on either side of one tire or behind the rear and in front of the front tire, you can pull forward to remove the rear chock and then back up to pull the front. My wife is the chock person when we are getting ready to hit the road.
Chocks are meant to be hammered in place with a rubber mallet to prevent any movement of the trailer.
IMO there is zero value to doing what you suggest. You would struggle trying to get a molded piece out. Bad idea. I wouldn't want that even if there was an adjustable mechanism. I want control knowing my chocks are tight to the tire.