Another option I'm leaving myself is to get a city van like the Ford Transit Connect or Ram ProMaster City, or Nissan NV200. Basically it's the smallest cargo vans on the road (US). These also are rated at 28-29 mpg on the highway.
Seems like a mini van or city van that is rated at ~28 mpg can do 30 mpg by pumping the tires up to rated max on the tires. If not 30, pretty dang close!
Oh yeah, I ran across this van that I just had to share;
69 Dodge Panel Van