YOU'RE DOING IT WRONG.
This is not a case of "Oh there's only two governments per starting type, boring"
It's a case of "Oh there's 15*2=30 types of government, ooo, diverse"
You're at a restaurant and you've got 15 choices, each of which comes with main and dessert.
It is missing the point to complain "This sux I only get 2 courses give me some choice".
The choice comes in picking one of the 15, not one of the 2.
Except that at the restaurant I prefer to make all choices at the beginning, then I can enjoy my dish without having to think about my next choice.
In a game, I prefer when I have choices to make during the game.
Making a choice between 15 government systems at the beginning is less interesting than choosing between 5 government systems at start, then having the choice between two possibilities each time. It's a bit like in Fire Emblem or some MMOs with branched class systems - there is a peculiar pleasure in planning the choice you'll make for your characters, that you can't find if you could only pick one class at the beginning of the game.
And the feeling of building your empire is stronger when it depends on choices you make while playing than if it comes from decisions you made at the beginning of the game.
It's true that 15 is already a lot, though.