1) The organ should be of a size and overall tonal structure that is completely in harmony with the size, acoustics and musical demands of the situation.
A less-than-satisfactory acoustic may preclude the tonal scintillation that could be achieved in a tonally superior setting, but it is no excuse for an instrument that is not beautiful and useful.
2) The organ should provide the major effects required by the musical demands of the literature as well as those necessary for assistance at worship.
An understanding of those requirements that is focused on musicality rather than historic idol-worship will permit design that can easily achieve both goals.
3) Every stop should be contributory to numbers 1 and 2 above and should be voiced for maximum color and beauty. When this is done, nearly every stop will serve both major requirements.
4) Technology should be applied when it makes musical sense to do so, not just because it can be done.
Geegaws and gimcracks are un-necessary in a well designed, cohesive instrument.
Flexibility is increased with beauty of sound and the intelligent selection and placement of stops, not with the use of more and more whing-dings, trade-and-service marked slogans, and the engineers’ latest gadgets.