Wait, so a pure 20 WF Wizard could get the Kensai PrE?
I'm presuming that this means that qualifying for a PrE would be more like how you qualify for a PrC - based on things like BaB, ability to cast spells, specific feats, etc...
I agree with this - imodifying FeatureB to fix deficiencies in FeatureA sounds like robbing Peter to pay Paul. If a pure class is lack-luster, improve the class itself.