As an alternative suggestion to a separate version of mIRC without an installer, seeing as how mIRC's installer already has several installation options (full, upgrade, & custom), maybe a 4th option (portable) could be added so that mIRC installs to the portable drive and doesn't create the registry and add/remove items.
This seems, to me, to be a simpler option as it would still mean that only one style of mIRC would have to be held on the servers/mirrors, rather than two.
