I suppose those are factors that would have to be considered by the Prime Minister at the time he made the order.
However, there is a risk that voters would be much less interested in voting if the choice they make is unlikely to serve any purpose in the near future.
Finally, I think we have to consider the impact this could have on the nominees. What is the point of taking part in a race or a campaign if there is no certainty of being appointed, even if you are chosen by the voters? I think that has to be considered, at least as far as the nominees are concerned, in this case.