Use the scoring system responsibly, or just abandon a scoring system entirely.

I find it interesting that you mention the Assassin's Creed soundtrack being in 5/4. To me as a music nerd, that completely took me out of the experience since 5/4 is completely uncharacteristic of the period. I've found that odd time signatures work great in in sci-fi games. Mass Effect and Portal 2 are great examples of this. Another kudos goes to the God of War theme. It's very Beethoven (Greek mythology was a common theme of his) but it's also the the phrygian mode, much more common on ancient Greek music than any other period.