All Passacaglia lovers:
How about this "problem"? Almost everyone stops after the "Passacaglia" proper (to cut the fullness of the Plenum back a little), then proceeds with the fugue. The ms doesn't have that, however. (I know it's not Bach's ms, but it's unlikely that anyone would make such a major change). My solution? I consider the Fugue to be the 21st variation, so resist the temptation to build up to full organ at the end of the Passacaglia proper. I don't resist the temptation after the Neopolitan chord at the end of the fugue, however! I think seeing this as a 2 manual and pedal harpsichord or clavichord work (which would remove the problem) isn't credible.
Food for thought?