[BrockNicholson]

If I was an extremely powerful mage and the country I loved and believed in was going to war I would support that effort however I could. I don't think battle mage is at all "unrealistic" beyond the part where its a wizard. Of course, if one were to think battle mages unrealistic, one could simply not include them in one's game.

I would think illusion spells cast at very high power levels could be quite useful. Screening advances and softening the enemy with terrifying visions. Also, any spell that allowed you to manipulate a large amount of Earth could have potentially devastating effects. Ultimately though, I think your battlemages would end up like artillery. They would be primarily used to destroy each other and probably have little impact on the battle.

If I were about to lead an army to war and had access to a poweful mage totally devoted to my cause, I would probably want a significant number of enchanted arms and armor. For all the awe and spectacle that direct effects on the battlefield would have, infantry that never missed would be even better.