I think you gave the answer yourself.
You need to depart IFR at night, regardless of the class of airspace. You don't need an IR or IMC rating to do this (but obviously a night rating).
The trick is the airspace, as C.I. has decided to be Class A for some reason (I'd like to know the reason actually). Unless you have a full IR, you can't legally accept an IFR departure in Class A, regardless of CAVOK.