WieWaldi The problem is not that there are those octave shifted clefs. The problem is how the symbol looks like.
Agreed. The two clefs we currently use for piano music look totally different and are immediately recognisable, which is very important when reading fast. If there's a clef change I immediately see which region of the keyboard my hand needs to move to:
(Beethoven op. 53)
I'm happy that we don't have more than one G clef. When reading fast, it's really easy to confuse the treble clef and the French violin clef, but happily we only use the treble. If we were only to use the French violin clef I'm sure I could adapt as well!