No generosity needed.... YS326, special-effect attacks covers this exactly. It's pretty well defined, and I don't see any reason why it wouldn't be possible to do with magic.
Well, that section specifically mentions weapons and refers to weapon ratings on YS202 - so I think significant generosity is needed to expand it to magic.
There's also the way magic works, specifically it
"is the focus of will to create effect". If the effect you're creating with the spell is non-damaging, having the skill roll cause damage is both counter intuitive and subverts the purpose of the spell...a can of worms I'd rather not open. (You'd have to start asking yourself just when a manuever spell will cause damage and when it won't...can it accidentally cause damage? Big can o'worms!) Mechanically, spells are either attacks, blocks, counterspells, hexes, or maneuvers. (See YS251-253 for what you can do with evocation and YS262-264 for thaumaturgy.) You can combine types or otherwise split power if you have enough shifts, but it's not a weapon...unless you make it one.