I finished rewriting my Squid SSL patch. It now applies against Squid 2.4-DEVEL2. You can get it here.
I changed my methodology this time around. Instead of the gratuituous hackery I was attempting to sprinkle through the various HTTP reader and writer functions, I added a read_method and write_method field to the fde struct and then converted all of the calls to read() and write() to calls to the methods instead. This allows me to override the calls with SSL calls, and also means that other odd read/write types can be added later if people so desire.
Please have a play and let me know. =)