I do think that double kings is a tad overpowered, but I think that's the case with most promoted specialists. For instance, I have never seen someone with two Security Chiefs lose an outpost. So maybe Bigred's solution is the best? I think you should have to earn that large of an advantage, rather than having it be handed to you.
On the other hand, it does make the game move faster. If I had two kings, I'd sure be playing more aggressively than if I only had one. And if I had two Chiefs, I'd sure be mining aggressively to capitalize. The same applies for most specialists. It's a huge edge that encourages faster play, which I think is healthy for a game like this.
"Can I make a suggestion that doesn't involve violence, or is this the wrong crowd for that?" -Hoban 'Wash' Washburn, Serenity