So, I don't think this has been suggested before, but I think it would be really awesome if you could create/hire units like the privateer in Civ IV.  What I mean by this is that you would be able to have/pay off units that appear to have no alignment.  I was thinking of a sort of bandit den or something...sort of like the pirates in sins actually...but without the timer...and you wouldn't ever know how much everyone else paid.  In theory they'd then send out bandits to attack whatever nation had a bounty on it's head, or the biggest bounty.  Alternatively a nation could by a raid with the price depending on the number/strength of the bandits to attack and maybe even choose the city.  This could be used as a distraction for a major offensive, but without the target knowing who hired them, or if they were hired (bandits are greedy, they don't necessarily need a reason) , it would make it hard to know where to position troops if you expected an attack.

        I also thought about having units, like privateers, that were actually user controlled but had no apparent nation affiliation.  It would be fun if both of the types suggested could turn on you too, to add a little risk .  I couldn't think of a good reason to explain why these troops wouldn't have an affiliation if they were user controlled, but I kinda like the first way better.

       Another thought was to have an ability/spell that would allow a sovereign to spawn in a monster den.  Monsters would be completely uncontrolled of course, but I think it would be an interesting ability none the less.

Sorry for the haphazard/unorganized nature of this post, I've never been very good at organizing my thoughts.