[tz] A New Rule? (was McMurdo/South Pole)

A partly-baked idea to solve the more general problem of when zones appear and disappear: would it make sense to have another kind of entry in the zone RULES column to indicate that we should now follow another zone's practice? How about the keyword, Zone, a space, and the name of the other zone, with the next column following whitespace, if present, being the [UNTIL] column?