If you're after a 700c steel roadbike feel, consider the Bike Friday Pocket Rocket. It's a steel, drop-bar bike that fits into a suitcase (that's just a couple of inches beyond airline limits so it's rarely if ever charged extra). It's got slightly larger ETRO451 20" tires than many other folders (which use slightly smaller ETRO406), which I think makes the difference in road feel.
They are a custom builder out of Eugene, Oregon, so it takes some time to get one built. But you can also buy used first for much cheaper to see if the concept will work for you. That's what I did with the bike above.
Best of luck