In 3.x, I will pack the extension source files in a single .tar.lzma file named as extension-src.tar.lzma under to ease maintenance as well as save space on the ibiblio server. Any source tarballs that are only available as tar.gz, tar,bz2, .zip, etc will be repacked as .tar.lzma to save space. Using lzma on exsiting gz or bz2 tarballs does not compress them further. So I will repack them as lzma. They can easily then with a file manager like emelfm2 be recompressed to .tar.gz or .tar.bz2 to be compatible with the build scripts included in the source. Often, neither links to the particular source tarball type or the tarball itself is actually included in the submission. And that is fine, they are easy enough to obtain. And I also figure that those who will be building/rebuilding extensions are savvy enough to alter the source tarball type to fit the build script's needs.
For gtk2, this changed the space requirements from a 19MB tar.bz2 file to a13.8MB. .tar.lzma file.
I thing using lzma for sources is being good stewards of ibiblio who is providing this space for free. But please state any objections.