Making it an iso is a horrible, horrible idea.
Not to say that having it as an option would be bad, but making it the main way to do something is...
Thinking about it, we're actually pretty close already. I'm using ZCManager, and it has an option to autoload the first quest slot. If you stripped that down to a single executable that would always load the first save file, you could package ZC with a pre-made save file that has the first quest loaded to what you want. If there were some way to make ZC close when you exited the quest, they'd never see the main ZC interface.