1. Banning players who are spying is absurd.
2. If swapping lands wasn't a viable counter to spying then the devs wouldn't have given you the ability to.
3. As a leader, I am one myself, we take on the responsibility of those we let in our group. If you didn't properly vet the individual in a desperate attempt to gain active members, then you should take the consequences of those actions.
4. You've been given solid strategies to counter-act spying, stop trying to ruin the gameplay of others because your too lazy to put forth the extra effort that is EXPECTED of a leader. By ruin gameplay, I'm referring again to spying (since some enjoy it, and it is not against the rules), and also limiting GNW vision of lower ranked members. A lot of people like to see whats going on, removing even that would reduce the amount of people wiling to join by some degree.