Its nice to see a great idea and it even nicer to see a thread with no arguments.
Just one thing though about the attacking of imperial legion caravans...
...This is 200 years after the last of the Septim line died, we don't know if the The Imperial Empire even exists any more let alone controls Skyrim is you look on UESPs Time line of the forth era it doesn't say anything apart from "NON OFFICIAL" stuff saying that there was a coo and Black Marsh and Elsweyr Broke off and Black Marsh invaded Morrowind and more crap from that book "The Infernal City".
One Argument against the Empire being in control is if it were there would be no civil war as the New Emperor or head of state Would decide who the successor is.
BUT looking at the trailer it looks like the guards maybe wearing Roman looking gear which is always a sign of Imperial influence.
I love you're idea though and hope to see something like it in the game. What do you think this Rangers Guild should be called?
Hmm. Rangers, rangers guild, the (generic fanatasy place) rangers, I don't know.
On the legion, if the empire has come to total collapse, it could be remanant factions. Doubtless some up and coming new guy will be trying to rebuild the empire, and sending the legion to the provinces. They don't have to be imperial, they just have to represent foreign influence, preferably imperial. I liked the idea of the imperial scouts earlier in this thread who acted as bounty hunters.