Thanks very much for the replies so far. Right, the Busoni Fantasia Contrappuntistica is a wonderful example! I was not aware of the work by Leighton of the same name, apparently even subtitled "Homage to Bach" -- it promises to be very interesting, too.
Here are a number of works I came across in addition to those mentioned so far:
- Busoni: Fantasia nach J.S.Bach alla Memoria di mio Padre Ferdinando Busoni (1909)
(the organ chorale prelude transcriptions are not in the focus of my question as they are in romantic idiom as works by Petri, Feinberg&co. --- to clarify: I love this stuff! just looking for new things in this thread)
- Sorabji:
--- Transcription in the light of harpsichord technique of Chromatic F&F
--- Transcendental Study #99 (also a free transcription of the Chrom. Fantasy I think)
--- Prelude for piano after J.S. Bach (transcription of the first movement of French Suite No. 4 in E flat major)
- Stevenson: Passacaglia on DSCH: Not sure if it contains explicit quotes from Bach (except for the BACH motive). However, no doubt it has a lot of influence from Bach anyway.
- Pepping: Drei Fugen über BACH (1944) - I haven't seen or heard this so far.
Of course, more or less strong influences from Bach could be attributed to countless works (including the Schosty 24), while many of the works mentioned so far make more explicit reference to this influence.
Edit: quirky, thanks to you as well. Interesting list on that site.
Btw, even though it's from well within the 19th century, large parts of Liszt's Variations on Weinen, Klagen, Sorgen, Zagen sound quite bold harmonically (not the ending of course

)
Any further hints/advice would be great.