These are really low hanging fruit:
Image files are suboptimally compressed.
(just examples, there may be better ways or programs)
for raster images and
for the vector images
I get the following results:
Raster: processed 269 files saving 277087 bytes ( 24% )
in about a minute
Vector: processed 1435 files saving 2.2 MB ( 56% )
in about 20 seconds
Results from a fresh download of 2.2.2 mac.
If someone could just once recompress those files in the devel-tree the
benefits should propagate from there.