It might be debatable whether the ram counts as a "weapon" in its own right (and even moreso, whether it's bludgeoning or piercing), but for the rest, it certainly seems so. The extra damage will be negligible, but the to-hit bonus matters a lot.
This is also supported by the way Multimissile is written - you can cast it on bigger missiles, just with an additional cost (as it's a multiplier).
I would approve of a Mostali "Catapult Trance" spell. Although I suppose proper Mostali are in an almost trance-like state in their tasks anyway.