The reconstruction of partly or completely "disappeared" organs sometimes poses unsolvable problems for the manufacturer.

Is it really worth rebuilding organs without sufficient historical details ?

Is it certainly a lot more reasonable to rebuild an organ if the following elements are at least available : the case, some stops, a wind chest and parts of a manual.

Is it possible nowadays to build an authentic copy of an organ which does not exist anymore ?

I strongly disagree to that ! It seems to be much more important to create instruments with an individual character in response to today's musical needs and perspectives by respecting historical substance still present. Nevertheless you will find the strong influences of its original creator.