Other MMOs have tools that allow them to transfer whole guilds across from one server to another. Guild transfers can be done if they wish to respect the players.
And I agree with the premise of the OP. Lets have light population Server merges FIRST, then Free Character transfers for fine tuning, and also Paid Character transfers as an ongoing option.
My server yesterday - I was the only player on Belsavis for 2 hours in the afternoon. There were 7 players in the Fleet at Midday. GET A MOVE ON !!!!