I just got the idea that it would be good when we had 3..4 buttons for setting some modes in the script, similar to the sliders. In Z1/Z2 you could for instance use a button for setting NFA compliance. Would that be useful?

great idea!

Yup, that makes sense. Better to have toggles or flags and enhance cohesiveness than maintain entirely separate files (e.g. -fx, -nfa etc).