I think there may actually be a rule (or a very strong convention) against naming cabinet ministers while an election is in progress.
Do you mean real cabinet ministers or pretend cabinet ministers as discussed above? If you're talking about real ones, no government is going to shuffle the cabinet during an election because it would make them look out of control. Of course there are situations such as the death of a minister where a new one would have to be named. There is no legal obstacle to this.