Traders can trade with other traders but since they share the same win condition it behooves them to trade with at least a few non traders to get a leg up on the competition. I do agree though that there's more work to be done to really get a better balance between the specialties but I'd like to wait until the combat changes and planetary control changes go in so we can see how the balance of power shifts before tackling that particular issue. One thing we've talked about doing for the researchers is to allow them to terraform other people's planets and share jump gates.