Combined stats seems like a long shot as far as imagery goes. With cavalry it's understandable, since horses are normally armored and such. Even monstrous cav is kind of a long shot though. I mean look at mournfang; the ogres are armored but their mounts aren't. But for simplicity it's combined, and it works. On the other hand, Skullcrushers make sense, as their mounts are pure metal. But saying a dragon gets the armor of its tiny little rider is far-fetched. Plus T7 elves on star dragons doesn't add up to me. Or zed dragons with red fury. I think monsters are too big to combine with already powerful lord stats.
Using BS for cannons makes sense though. A "miss" can scatter away from its intended target. And then it still bounces in a straight line from the cannon. Bolts and cannonballs should probably hit the monster though, doesn't make sense that they'd hit the tiny rider in comparison to what they're aiming at. And in combat, it seems weird to be able to allocate attacks against the rider--he's so high up, how do you hit him with a sword? Do they throw their swords at him? This isn't a problem as much, as most people will attack the monster anyway for easier CR.
If GW does combine monsters to their riders, their Terror won't affect units, it'll affect players :devil2: