Seeing as how it's a demo, I would avoid lots of upgrades. It still has to be very straightforward for people to understand. And you certainly don't need 100-point builds for a demo. If the goal is to get people interested, then you have to sell them on the idea of the system, but you really want them to pick up a core set that night. Go with Luke + R2-D2 - instantly recognizable. Match him up against Mauler Mithel and Night Beast. They'll get a feel for basic game mechanics, pilot abilities, and upgrades. Plus, it all comes in the core set.
I'd wrap up the demo by simply showing them the other well known ships with one or two remarks on each one. Like "Here's the Falcon. You can pick Han, Lando, or Chewie as your pilot. It fires 360 degrees. Here's Boba Fett in the Slave I. Here's Darth Vader in the TIE Advanced. He gets 2 actions. Oh, and here are a half dozen other cool ships you can add to your squads."
I agree with you about concentrating on getting them to pick up the core set, so using just core set components is a good idea.
I was thinking a Han & Luke vs. Boba Fett & Darth Vader thematic" matchup for newcomers:
Luke (28) + R2D2 (4) + Marksmanship (3) + Proton Torpedoes (4) + Hull Upgrade (3)
Han (46) + Nien Nunb (1) + Expert Handling (2) + Shield Upgrade (4) + Concussion Missles (4) + Millenium Falcon Title (1)
Darth Vader (29) + Concussion Missles (4) + Squad Leader (2) + Hull Upgrade (3)
Boba Fett (39) + Assault Missles (5) + Daredevil (3) + Engine Upgrade (4) + Proximity Mines (3) + Ion Cannon (3) + Gunner (5)
There are a lot of upgrades, but with only 2 ships per side I was thinking that it would actually be a good showcase for using the different upgrade abilities & weapons.
I agree that this is also a feasible solution though, that is also very thematic. I think a combination of the two in some way may work.
I think I could set up a couple "beginner" demos using what was suggested by cordeiro and an advanced table using the build by gulik23 in case people are really curious about flying bigger ships.