Well, not sure if you've ever seen HBO's "Rome", but that show managed to show a variety of perspectives and stories from the Republic's transition into the Empire. You had the big players like Caesar, Octavian, Antony, etc., but also had intertwined small characters (namely two soldiers, Titus and Lucius) and therefore got to see everything from the pivotal political power moves to more "regular" Roman life. In short, you got a lot of exposure to various aspects of the Roman world of that time.
I'd like to see something similar in the late 4th-late 5th century. You've got the big players again, people like Stilicho and Alaric, plenty to go off of there. But then you can also focus on the more average people, because I feel as though regular life in that period isn't considered as much.
I thought it would be interesting to have two friends, similar to the dynamic in "Rome", that are both soldiers. One would be a native Roman legionary; there you've got the whole dynamic of being part of a shrinking and dying army whose soldiering traditions go back to the great legions of the Empire but now are shadows of their former selves. The other would be a foederati, a warrior serving the Empire on his tribe's behalf, but not really a true Roman soldier.
The tension between them would be the whole idea of one being a native Roman and the other being a barbarian foederati. Then, if it takes place at least during Stilicho's execution and the mass murder of Gothic foederati, that could pit them against one another.
Just random ideas really, but interesting to think about!