By allowing free transfers with a cooldown of about a week between same type super servers such as PVE to PVE or PVP to PVP you would let people consolidate.

At first it would cause havoc. In some cases everyone would rush to one server, but then people would flee the queues, and it would rock back and forth until settling with a somewhat even community between the two servers.

This way you wouldn't have server envy and people could consolidate all their characters.