You know, I imagine that one of the few circumstances and ways in which battle magic is 'safe' to cast...
... is with Slann Mage-Priests casting through Skink Shamans.
The reason for that being: literal ablative armor. The Skink tanks the backlash or miscast and pop goes the Skink, in place of the Slann.
(And also. Was it Skaven Grey Seers or Dark Elf Sorceresses that could use slaves to shunt Wounds received, onto the slaves instead? I remember that combo of things coming up in Ulthuan Quest, but since it must have combined two things, that means that one of them must have been the "have slaves tank a Wound" thing.)
I could also see something similar for Necromancers and "bound souls" or the like. (Though... that might just be a Necromancer-flavored Grounding Rod, come to think of it.)
So yeah. There might be a way to sometimes avoid paying the full risk or cost of battle magics... ... and it's by making somebody else pay it in your stead. And even then, I can imagine that it still might give the Slann a headache if their Skink blows up.