Suggestions
When a warmage gains access to a new level of spells for his class, he automatically knows all spells for that level listed on the warmage's spell list, as well as one evocation spell chosen from the wizard's spell list of that spell level or lower.
Doing this under the "Spellcasting" header could replace Advanced Learning (leaving a vaccum for more abilities) and grant the warmage up to 9 evocation spells from the wiz list.... or even more if he gains Improved Spell Capacity feats. Plus... doing it this way also helps if the warmage decides to enter a prestige class.
Warmage Edge (Ex): A warmage is specialized in dealing damage with his spells. Whenever a warmage casts a spell that deals hit point damage, he adds a bonus to the damage dealt equal to the spell's level plus his Intelligence bonus (if any). For instance, if a 5th-level warmage with 17 intelligence casts fireball (a 3rd level spell), he deals 5d6 points of damage normally, plus an extra 6 points of damage due to his warmage edge. The bonus from the warmage edge special ability applies only to spells he casts as a warmage, not to those he might have by virtue of levels in another class. etc etc etc
This way the warmage edge feature could scale slightly better with the power of warmage spells.
To fill the void, you could incorperate ability options chosen from a menu like the rogue.
Consistent Edge (Ex): Whenever rolling damage for a spell that benefits from your Warmage Edge class feature, you can reroll any natural result of 1 on any number of damage dice. You must keep the result of each reroll, even if it is another 1.
Resonating Edge (Ex): When casting a spell that benefits from your Warmage Edge class feature, you may reroll any attempt to overcome a creature's spell resistance. You must keep the result of the reroll.
Warded Edge (Su): When you successfully cast a spell that benefits from your Warmage Edge class feature, you gain temporary hit points equal to that spell's level plus your intelligence bonus (if any) to a maximum equal to your caster level. These hit points last for 1 round. Hit points gained from multiple uses of this ability do not stack.
/////////// other suggestions //////////////////
What about giving them the battlecast ability (with warmage spells only) from the Havoc Mage PrC (miniatures handbook)?
And give them medium BAB?
Expand their skill list to include ride & handle animal so they make good on their role as mobile artillery in the battle field?
Give the warmage an exclusive spell or spell-like ability that grants himself and allies SR against the spells he himself casts as a warmage?