[VBprogrammer]

I'm not sure where you draw the line though? None of this is new, making modifications to existing designs is the aviation equivalent of developing a new feature. Hanging new engines from an existing fuselage, replacing the avionics and lengthening a fuselage have all been done before with reasonable results. Conversely, clean sheet designs have had terrible safety records initially.

Asking a manufacturer to make a clean sheet design every time they make a change is probably going to result in more accidents than it fixes (see the bathtub curve).