I recently downloaded this mod, and I am impressed with how geeky it is with implementing better footstep sounds. As an audiophile, this is the kind of mod I love. But I have noticed an issue with the glass footsteps.
Every time I step on glass, it makes the same sound, slightly pitch shifted. In reality, glass has a wide range of sounds depending on how big the piece of glass is. It depends on the resonant frequency.
Now, I get that calculating resonant frequencies is an np-hard problem, but Minecraft has made it easy on us by making it voxel-based. Instead of taking minutes to compute the resonant frequency, you could estimate it with a simple equation:
pitch.glass_sound = c/b^2
Where c is a constant that can be fine-tuned to perfection, and b is the number of touching glass blocks of any kind, since the color of glass shouldn't change the resonation pattern. This should work, because resonant frequency is inversely proportional to the volume of the glass.
This could also be implemented with glass panes, though the resonant frequency would be higher because of lower volume.

Another feature for glass that I would love would be to dampen the glass sound if surrounded by full blocks. That way, glass buried in the ground wouldn't ring, it would make a dull tapping noise instead. If the glass was out on the open, it would ring instead.
I hope my ideas will make this mod a little more feature-complete and interesting.
Sincerely, AnonymousBeef