Personally I do place tonality ahead of spatiality on my list of priorities, but tonality was not the topic of this thread. In general I agree with the approach of fixing first that which matters most.
you say that but your focus is and always has been off axis response. That is your holy grail. The problem is its not hard to do what you so eagerly seek to achieve. Cheap dsp speakers costing a few hundred bucks can give you smooth perfect off axis response if thats the goal.
So even if your goal was the key to perfect sound, it has already been done and very cheaply at that.
your injunction to "forget about the off axis response" overlooks a vital aspect of tonality:
No it does not. My definition of tonality is completely different than yours. Tonality, according to my definition is the area well below the crossover point. So it has nothing to do with off axis response.