My Python script is for converting .aupreset files (as used by Logic for saving presets) to .fxp files, and it only works for plugins created with JUCE, and probably won't work for other plugins. Here's why:
Audio units save their state into a "CFPropertyList" and JUCE adds a specific key ("jucePluginState"/JUCE_STATE_DICTIONARY_KEY) to store the data block returned by the JUCE plugin's getCurrentProgramStateInformation/getStateInformation. (relevant code at juce_AU_Wrapper.mm, JuceAU::SaveState).
My script looks for this specific key in the .aupreset file.
I'd look in Kontakt 5's returned state to see if they too save their state in a block in the property list (the AU host-side code in juce_AudioUnitPluginFormat.mm, AudioUnitPluginInstance::getCurrentProgramStateInformation encodes the CFPropertyList from the AU into a MemoryBlock, you'll have to decode it back to look..). If they do, it shouldn't be hard to convert Kontakt 5's state to VST, but this wouldn't be a generic solution for all AU plugins.