I agree that they are poorly written but not that poorly. Clarification is needed, but GW is notorious for lacking clarity. And yes, these missions are $*@(!*$@.
It says he gains the IC special rule and his profile is replaced by the following following profile is replaced. So yeah, the deff dread could be put in a rhino, why you'd give your opponent a 75 pt model I don't know (if I were playing Orks they'd get a standard boy). It wouldn't have an AV anymore, it would simply act as a new unit with that profile.
And dedicated transports aren't troop models, they are dedicated transports.