Yeah, who among us hasn't razed a city in a game of Civilization, or glassed a planet in a game of MoO? We generally carry out political policies that we wouldn't dream of endorsing in real life.

In games like these, the political themes are generally kept in the realm of hyperbole, so I don't think introducing such themes would really turn anyone off. I don't think we're talking about having options as subtle as Campaign Finance Reform or Estate Tax in GalCiv games.

Like others, things I'd like to see:
a) Make approval a little trickier to manage. Right now you can prevent low approval effects easily, with the tax slider. Add in a few more elements that are less easily controlled by the player.

Limit the rate at which the player can change tax rates. Perhaps only X% per turn. No more wild swings in the tax rate, which are unrealistic.

Have much harsher penalties for low approval. If an opposition party gains power, perhaps some of your colonies use their newfound influence in the Senate to secede from your empire.