In the end, unlikely that any of this talk about one peculiar
harpsichord tells about the WTC - even if we accept the Bachhaus
instrument as a good sample of what was around Eisenach c.1700, JSB
was on the move soon afterwards to many other instruments which
probably differed much more than today's, at least those today
(Has anyone recorded it on an 'Italian' hpcd?)
The multiplicity of possible WTC instruments doesn't rule out
specifying that Bach was thinking of definite tonal characteristics -
particularly concerning the balance between registers and the
possibility to have several different timbres at once.
On matters of style the pieces are really widely divergent - within a
single tonality you find a 'French' broken-chord prelude rubbing up
against an 'Italian' ricercar-like fugue. Even with Robert Levin's
idea of switching between instruments, one instrument is pressed into
very different modes of operation and the difficult task is to choose
it and use it to suggest the various (incompatible?) ways in which
different styles sound individually excellent.
Enter Graebner, Mietke, ... ??