OK, I'll bite - what happens when you get to the Ab Prelude, with its
scale of Bbb major?

Or the D#m Prelude with its Gx, Dx etc?

Naturally you *could* retune the B# keys to Cb, E# to Fb, A# to Bbb,
D# to Ebb in the first case - or the Gb to Fx, Db to Cx, Ab to Gx, Eb
to Dx (etc.) in the second - but doesn't that rather defeat the
object.

Or you could use 1/3 comma meantone all the way through, where these
notes are equivalent, but chords are going to sound pretty alien.

At least WTC doesn't contain any enharmonic modulations.

~~~T~~~