The emission problem of VW cars seems to make the company confront to very difficult situation.
Any reformed application for controlling the engine may trade off the motion performance of the car. The customers won't agree with that. It is not practical to exchange the engines to newly developed ones for total 11 million cars.
The only possibility is buying back all the sold cars. Buying back all of them may cost over one hundred million USD if they pay half of the prices. I wonder if VW could put up with this financial burden.
This event showed how risky it is to sell items with the same parts and spec all over the world. Once such a problem as this VW case occurs, it may give them astronomical monetary burden.
Considering of the stern competition for better emission or gas mileage of automobiles, I am afraid there could be such a case of corruption in this business field as this VW case. I am afraid the engineers on charge of designing may be too much tempted to alter such an application for apparently better performance.