We already know that with the Civil War going on, political tensions have burst. Being able to assassinate members of the opposing party would be awesome, assuming, of course, we get to pick a side.
EDIT: Its late, I forgot the Fake ID part. Sorry.
So, to make being an assassin feasible, I propose these ideas:
Smoke Bombs-Mapped to either hand, these would obscure the vision of any guards following you, allowing you an easy escape. This seems like it would work perfectly with Radiant Story, with guards reacting to the smoke with confusion. This would attract guards to the scene, however, and would only be effective as a distraction.
Disguises-Similar to the Faction Outfits in FO:NV, these could vary from guard armor to the robes of scholars, and equipping one would decrease the chance of the guards recognizing and arresting you. The chance of being discovered would increase or decrease based on both the "power" of the disguise (i.e, guard armor is more effective than monk robes) and your bounty.
Crysis 2 Style ledge-grabbing-You've had it happen to you. You can't reach that flat ledge an inch above your character, because its beyond him to grab the ledge. I'm not sure if this is possible to implement in a game like Skyrim, but it sure would be nice.
So, those are my ideas. Leave feedback on those you think need work, or blatantly say they svck. You decide