NOT easy
To be certified by the FAA in the US, Van would have to make some really significant changes, almost certainly leading to an overweight and grossly expensive death of what was a great airplane.
The design would have to comply with FAA part 23, which prescribes structural, aerodynamic, performance and maneuvering requirements among other things. There are a few things I *know* would have to be changed to meet Pt23. I won't throw a laundry list out here of what I think would have to change, but it would be a
mess. Of course, all the materials used also have to be certified, or meet requirements. Doing all this is a GIANT job.
In 1994-5, as an engineer at Kestrel Aircraft, I only came into contact with certain parts of meeting Federal rules standards. But, I personally had FAA certification authorities apply their
own personal design criteria while meeting for preliminary design review. Been there first hand. Quote: "We won't certify it unless you don't do it this way" (specifically, pitch trim system, aileron control system, composite fabrication process to name a few) Lesson: give the government room to interpret the rules, and they will do it to their own advantage.
We blew through about 25 million getting one prototype in the air, and built all the jigs for it, only to have FAA tell us we didn't have adequate head strike room in the cabin. It was a disaster. Good thing I had resumes out for another job...
Here's a pic of the airplane, which was pretty close to a C182 reverse engineered in composites:
