Yeah, flutter analysis would be more than a little work, and very little return on investment.
So if IAS Vne is a holdover due to lack of instrumentation, as you say, why perpetuate it?
As has been detailed many times in many forums, aircraft design is ALWAYS a compromise. Van struck a wonderful balance but it is still a compromise. If you are looking for an aircraft with a high top speed and flight into the higher altitudes, the solution is to find a different aircraft that was designed FOR that mission.
Someone once said that the best way to increase the speed of a C-172 was to sell it.