That's like saying the wizard can have all the benefits of being a warmage by carrying around dozens of attack scrolls and wands.
Warmage deficiencies:
Buff - Scry - Teleport tactics: the warmage fails all three. Well, Legion's Fireshield is pretty good, but kind of lonely by itself.
Defensive Magic: the warmage has Fireshield, better HP, and can wear armor. The normal arcanist has fireshield, stoneskin, False Life, Spell Turning, armor and shield bonus spells to make up for lack of normal armor (and stop magic missiles), Contingency, mirror image, resist elements, etc. The warmage's ability to take or avoid damage is inferior to a bard or rogue.
Debuffs or enemy crippling spells: Ray of Enfeeblement, Slow, Enervation, Confusion. These spells generally have no save or attack Will. Since many monsters have crap for Will saves but lots of HP, these spells can be very effective. Also, they tend to especially gimp certain enemies. If Trolls or Girallons are attacking at Claw instead of Claw, Claw, Bite, Rend (Claw, Claw), then they pose little threat to comparable characters; hitting 3 out of 4 with slow has a greater impact than hitting each for 1/3rd of their HP. On the bright side, the warmage does have the Waves of X line of spells.
Battlefield Control: Various Wall spells, Force Cage, Grease, Web, etc all deny areas to the enemy or split them into sub groups. The Warmage has few spells here (Stinking Cloud, Evard's, and some Prismatics), but they lack some of the better ones.
Detection: Not only scrying, but no Glitterdust, See Invisible, Moment of Prescience, Detect X, etc. In other words, have fun fighting Invisible people - especially since it's usually the wizard's job to notice those guys.