It would be a major redesign effort to swap an engine's regular fan blades for wide chord fan blades. In addition to certifying the new fan blades as well as the new fan hub, the fan containment system would have to be recertified and that would mean a blade out test. The blade out test is the last test of a cert program because when the blade is released even if it is contained, the engine is destroyed. And since the mass of the fan rotor would likely change, does the front bearing support and the front bearing have to be changed. Because the wide chord fan blades may turn at a different speed, the low pressure turbine rotor may have to be rematched to the fan. Then there are the usual gamut of certification tests like durability, operability, icing, etc, etc, etc. It would be a very big and expensive effort for a retrofit program that would be risky if the operators don't buy it.