"Go suck yer blade!"
Impossible to tell until the game becomes available in the UK, although having reading the rules I would be concerned about the number of actions in between each Doge election.
What do you mean: that with 5 players the amount of actions (=dice chosen) would be too high? In fact, usually in a 4-players game there are 9 actions (2 rounds + last round of the current Doge) between elections unless Assassination card is played.
In a hypothetical 5-players game, in most cases there would be 11 actions between two elections (9 + 2 actions by the fifth player).
If I'm not wrong
...it would mean probably 1 or maximum 2 less elections in a full game. If the concern is about candidate choice mechanic becoming less important (and election winning becoming MORE important), it would affect all players the same way...
ERRATA: the "action count" was based only on the first round of play. In subsequent rounds, the amount of actions played varies between 5 and 12, depending on the Assassination card (ok, there's even a slight chance to have TWO assassinations during the same Dogado..) and on the position (around the table) of the player becoming the new Doge. If a player manages to win two consecutive elections, the "life" of the second Doge will be longer (12 turns without Assassinations). With a 5th player involved, the additional actions would be 2 or maximum 3 per Dogado.