Actually, Chris Johnson has a good point here.  Ya, this is a nice ship and design, but I would think during war, the Federation would definitly NOT want their president in a powerful ship at the front lines.  The Galaxy Class (or perhaps a hybrid of it) would be a much more logical choice for a Presidential ship in my opinion.  Granted, the Galaxies are not the most powerful ships in Starfleet now, but they have excellent Hull sizes which means they can load up on a lot of other important equipment then just weapons.  You could load sophisitcated Scanners, Sensorsr, Steller Cartography Computers, Fleet Tactical Rooms, Huge Facilities to coordinate Federation Operations and Civilian Trafic, etc.  I mean, the Galaxies can carry nearly 6000 people comfortably, I think a Galaxy with all that extra space would be the most ideal choice for a presidentail vessel.  
Granted, the vessel would have some armament on it, but I would imagine it would have the Standard Phaser Arrays with a more of an emphisis on Defense and Sheilding then offensive firepower.