All its going to end up doing, is giving people who joined early, and unfair advantage to anyone who joines during tribal wars.
Your going to make players down the road deal with a high risk world, and all these tribes now will have had many months of safe growth. No new tribe is ever going to be able to compete with a tribe that had the advantage of safezones.
No one sees this as an issue down the road? Unfair advantages are UNFAIR. Even if they benefit me as an early joiner.