I would bet on a list of fictional monarchs for the lacking monarchs rather than random ones. In EU3 it was brand new code, I think, so unless they manage to write their own code for this, there would be nothing in the "old" EU2 code to make this possible.
In this case I do hope that the AI is coded to use the foreknowlege about monarchs and events as the human player can. Nothing like waiting a month or two to build a factory because the upcoming monarch has better stats.