Consider:
Close BT, migrate to Dwilight (the only testing island left). Close Colonies, migrate to other stable islands.
If the Zuma can be replaced, not assumed, by players, a lot of Zuma specific code can be removed. (Outer Tilog)
Result:
3 stable islands and 1 testing island left (I recommend making Dwilight immigration-only like BT so new players can concentrate on stable islands).
