I have actually never gotten the "expansion" variable to do squat. I set it to 0, or 1, and I look like an old classic toon - but I can still port to wherever I want. It is a most undocumented feature.
But a clever way to emulate progression-by-deed is to implement a "flags" system on expansion zones. Do _this_ quest, get _this_ flag, zone to Kunark. Tada.
Show of hands... how many just love flagging?
