This reminds me of the Dominions series of strategy games.
It's a battle Turn based 4x fantasy heavily based on gods, priests and mages.
There are many spells in Dominions. However there are many mages in there as well. However in battle many mages lack natural defense and offense. In their robes and armed with sticks, they are squishy and limp. However casting spells to boost their base offense or defense is often bad as it exhausts them.
But some warriors are spellcasters. They don't need spells and blesses to be killy tanks. They start with good offense and defense stats. The spells just make them scarier. The spells can be focused boosting and utilizing these stats. And some spells useless to a robe mage are scary coming from a glamoured elf or tanky legionnaire. No need to waste slots and power on AC and speed spells.
The swordmage would be that strong agile and tough mage who can and would cast those niche combat spells as well as know the same utility spells of a wizard or sorcerer.