Shock troops: a battalion of rat soldiers used in serious conflicts. Nickname: "The Iron Rats"?
Partial success on spell-casting: spell goes off at 1/2 of your Magic rating as its power. If your Magic rating is negative, the spell just fails... or maybe you should double it, so that technically gets cast, but so pathetically that it hardly matters?
Fail by 5+ is crit failure (e.g.- in combat, lose next action or drop weapon). Fail by 10+ is crippling failure (e.g.- hit friendly, break weapon).
Languages skill is specialized, but can be applied to figuring out tongues that you don't speak. Most languages will share a common root, since they're inspired by the same magic. The only truly alien tongues would be ones invented by non-magical creatures.
Crossbows can be used untrained. Bows require at least a +1 in an appropriate Missile Weapon specialty or you only get to roll 1d10.