well the ssl session is between your client and the destination, your proxy having access to the contents of that would form the basis of a man in the middle attack, generally not something a user with a supposedly "secure" session will appreciate. squid 3.0 does appear to have a larger amount of support for this...
http://www.visolve.com/squid/squid30/network.php and then i assume it'd just plug into the AV as normal. Note that as you have seperate ssl connections on both sides, you have to use your own SSL cert on the inside, which your clients maybe object to - you clearly can't pass on the original SSL details, so have to provide it yourself. If this isn't only for personal use then you need to be *really* careful. you want to avoid terminating numerous types of connection, e.g. online banking. if this is in a commercial environment and users find you've potentially had clear access to their bank details, they'll quite rightfully want your head on a plate.
