If we do get a Jedi Luke, I would think it would make sense to require a whole PILE of characters to get him:
CLS (obviously)
R2 (who you have already if you have CLS, but still)
Rebel Officer Leia
Captain Han
Raid Han (yep, two Hans)
Chewbacca
Han's Millennium Falcon
C3P0
Wampa and Hoda (they said GEC characters would never be requirements for anything but I could see them reneging on that)
Lando Calrissian
Wedge, Biggs & their respective ships
A future-release Red 5, probably
And...wait for it...Darth Vader. To face off together against EP for the very last stage.
It's more likely to be a "hey buy a bunch of new stuff so you can get the King of Arena" type of deal, sadly, but it would be cool to do it this way - some of the characters are old and widely owned, yes, but you'd also be required to have a bunch of legendaries, which I think could spur some spending from people who decided to skip certain ones. Plus I'm sure most people haven't bothered with Capt Han, and newer players probably don't bother gearing up old characters like Lando, so you have that going also.