In the books Harry specifically says that Wardens carry the swords because they're not allowed to kill with magic...
Sure, but that doesn't explain the use of guns, swords, and grenades in actual battle (something that clearly occurs...look at the fight scene at the end of Dead Beat. Or the duel in White Night).
Also, Luccio uses her 'needle of fire' as her weapon of choice, which Harry describes as "fire magic not unlike my own, but infinitely more intense and focused and far more energy efficient." I think if you have Epic control, a 4 shift rote without stress is reasonable. It seems fairly standard for more experienced casters to be able to do that kind of thing.
Luccio does precisely that...but I'm not clear that she doesn't take Mental Stress from it. The 'more energy efficient' might just be noting that she does 9 shifts of energy without frying her brain or the surroundings. She certainly uses it infrequently enough that that's what it could be. Also, she likely has a Power specialty of at least 3, so even if you want it to be Stress-free it's doable with my suggestion.
What we
don't see is Ramirez using such things when he's low on energy...we see him either dissolving things with Weapon: 6 entropy blasts or shooting a gun, which considering it's Weapon: 3 and he has only Fair or Good Skill, makes no sense at all if he could do Weapon: 3 Water Evocations with his effective Skill of Fantastic.
Also, if you're going to base it on specialisations rather than Spin, surely Control makes more sense than Power?
Not really, no. The point is that you can channel X power so easily that you don't even take Stress. Power Specialization makes more sense for that, as well as making Power a bit more useful (which it needs more than Control does).