I have a theory involving Ven, the scans, and the FM+ secret ending:
Ok in the scans a guy looking exactly like Roxas is wearing a armored suit, and it appears that this person looking like Roxas can summon someone out of himself(the brown haired guy who is holding Roxas, who passed out). Now in FM+ secret ending someone walks down a hallway and looks at some armour and says, "It's been a long time friend" or something along those lines. Now I'm thinking that guy is the Roxas looking guy, and when he wears the armour he has the power to summon the brown haired guy. And somewhere in the scans someone translated them and it had a quote of someone saying:
"Please don't depend on me, just erase me....friend". so what I think is that Roxas locked him up in the room(Birth by Sleep is a prequel, and they did say that the secret ending from FM+ might be an ending scene in BBS) and later on he goes back down and needs help from him, or he's just visiting "it". Now thats the end of part one....
Now I think that the thing in the armour is a younger version of xehanort, or xehanort's heartless because there physical traits do match...(face formation, eyes, even hair, it's just that the back of his hair isn't as long)and this would also explain how Zexion and the other organization member in FM+ were chatting about how Xemnas built the long hallway room and started talking to himself. But of course there are alot of gaps in this theory and there are endless possibilities, there is a tiny chance of more than 20% of this post being correct, oh well...hehe