Sense on the Nexus 7 would be awesome. I know it can be a battery/cpu hog or whatever but seriously, I'm pretty sure the Nexus 7 could hardware could handle it. Sense has so many nice features that I miss. The UI is gorgeous (subjective, I know), the included widgets are fantastic especially the clock, and small things like the fact that navigation is linked to calendar events so you can just bring up an event in your calendar and then click on the location and it will take you there.
Edit: nearly forgot to mention the great music player, and the latest keyboard is main thing I miss.
Have no idea if it would be possible, but I would LOVE to see a sense rom for the nexus. What about a ported Flyer rom? I have no idea about development though so forgive me if it would be impossible.