I like them as either arcane artillery (the typical evocation/abjuration blaster) or magically enhanced operators (elite tanks or scouts/infiltrators with low level specific arcane training to boost their skills).
Logistics wouldn't really be a *war*mage thing, because abjurers ought to block the ever living shit out of that when armies start nearing each other or when armies approach fixed defenses, so it would basically be the same kind of expertise as civilian casters.>what about gishes
Fuck them. Specialization rules, gishes wouldn't have the experience to be real fighters nor the education to be real casters. There are only 24h in a day, and only so much energy for training. By the time you've learned everything you're 35 and you're closer to retirement than enlistment.
I guess it might work for very long lived races, but really any society with longer than human lifespan ends up being the holy empire of handwavium anyway so just do whatever and hope your audience likes it.
One other exception would be the dilettante (basically bards): No pretensions of being the ultimate mix of swords and sorcery, just a plucky amateur picking up anything that can help him in his quest for whatever. Only really combat effective by virtue of being a pc/heroic adventurer, not something that works as a standard training option for armies.