Just to give you guys an idea of how much Finn's story in TLJ let me down, here's the speculation I had collected and imagined from over the Internet and other discussions on Jedi Council Forums (aka, the guys whose site keeps crashing for me right now):
- Finn was going to get deployed to infiltrate the First Order, like he did, but with a point being that his knowledge would allow him to navigate through their world.
- Finn would team up with Rose because... reasons (I presumed technical expertise to sabotage the Supremacy or help steal a vehicle), and he would have to put up with the exagerrated version of his heroism throughout the story, eventually, of course, becoming his own legend.
- Finn would seek out DJ, a smuggler in First Order space, in order to get the materials to complete his infiltration. The stop on Canto Bight would be very short and not take up that much time; Finn was going to spend significant, non-action scenes with the First Order.
- While Finn, Rose and DJ start to complete their missions, with DJ's possible threat being made clear and even making Finn wary, they run into some people who knew Finn. Since the FO covered up that he defected to prevent it from spreading, Finn now gets awkward bonding time with old friends.
- PS, the above rumor actually came with a suggestion that Tom kriffin' Hardy would be that Stormtrooper.
- I presumed they would of course expand on the implications of Finn being an enslaved child soldier, because why the hell wouldn't you? (Oh, poor dumb me.) He'd find himself conflicted with his old friends and viewing the FO through new eyes, now getting righteously angry at the FO's kidnapping of small children.
- DJ would inevitably sell them out, Phasma, now with some context for her relationship with her men and Finn in particular, would order the executioner Stormtroopers to behead not just Finn and Rose, but also his old friends-- can't let that defection infection spread!
- Luckily, Finn and Rose prepared ahead of time, activated an explosion fueled distraction, and start a riot with (very few) Stormtroopers vs Stormtroopers in the hangar of the Supremacy.
- Finn faces Phasma, but now filled with some clearly righteous fury at her for being the personification of the system that raised and brainwashed him, and beats her, like he does in the film, but now when he leaves, there's an element of inspiration and mythos that we see has entered First Order ranks...
- The film ends with the Resistance on the run, yes, but Finn now has stepped up, and while he may not be a Force user, he's damn cool!
Yes, I know this is literally a textbook definition of being overhyped and overexcited for something that won't happen... But I correctly predicted the Praetorian scene with my buddy, so I do feel snubbed that I so overestimated the awesomness of Finn's story elements.