Since New Terra's magnetic field is in flux, that would probably play havoc with such a system. Plus, more is required to deflect weapons fire other than magnetism. Magnetism would not, for example absorb or deflect laser fire unless it was of a magnitude greater than that of your average star. Even the magnetic force required to deflect a steel ball dropped gently to the ground would be massive. Even if you could generate such a field, you and any structure would be destroyed if located in or around the field.
The best method for shielding is the traditional kind. Ablative shielding for energy weapons and heavy armor for kinetic weapons.
Leave energy shields to the realm of less accurate games like Supreme Commander or C&C...