As far as I know the guy in the Storm Trooper armor is just wearing it as a disguise, and is actually a Jedi(and possibly our main protagonist). A reference to the original trilogy probably.
No evidence of that! That's just speculation!
I'd much rather he was an actual Stormtrooper. Ever read Timothy Zahn's Hand of Judgment... duology? Allegiance and Choices of One? Both awesome! Focus on a quintet of stormtrooper deserters and Mara Jade.
...thooooough to confess, if they'd just scrap the whole Force Awakens thing and replace it with movie versions of everything Timothy Zahn ever wrote in the Star Wars universe, I would be the happiest nerd boy ever.
As great as that would be I really can't see it happening what with the canonical changes to the mythos. Disney's recent announcement has uncanonized a hell of a lot including Kotor, Force Unleashed, & a lot of games and books. Infact anything not under the legend banner isn't considered canon anymore, that's to say only the movies, and the two tv-shows, and anything released after the Disney announcement is still canon.
Here's a link to everything still officially canon. Everything else is expanded universe and non-canon.
I loved the Dark Force Rising trilogy. I might have to read more of his work. I don't give a rats ass what Disney says. They can choose not to include any content from the expanded universe if they want it's their loss. As far as I'm concerned it happened. I think that Disney would be better served by working what they can from the expanded universe into cannon and leaving the rest to speculation. Putting out and official DIS of the expanded universe it lame.