I've figured out how SECRET EMPIRE is going to end. It all goes back to SECRET AVENGERS I#11-12. In these issues by Ed Brubaker, Captain America uses a machine to try and figure out why WWII hero John Steele went back and joined the Shadow Council. This machine connected to the Vanishing Point, a portal that leads to other places in space and time. With this machine, Cap was able to see John Steele's memories and watch them play out on a viewscreen. Well, Steele's memories are fragmented, but Cap remembers the last mission he and Steele went on, the mission where Steele vanished afterwards. So Cap hooks himself up to the machine and adds his memories to Steele's. At one point there was trouble and Cap had to be pulled out. Steele finished remembering on his own.
I posit that the second Cap being seen in the SECRET EMPIRE series is actually a part of his consciousness that had been left behind in that machine. This is the consciousness of Cap when he was good, heroic, and all that, untainted by anything. That bit is making its way to Nazi Cap, and by the end of the storyline, it will merge with Nazi Cap's brain, thus restoring Cap's mind without any foolishness like using a cube to fix him, or anything else. There won't have to be a reset button. We'll have Cap back tothe way he was but he will still have to endure his actions over the past year or so, as will his associates, friends, and fellow citizens.
The first sighting of Vanishing Point was in SECRET AVENGERS I#3, when Major Aloysius Thorndrake of the Confederate Army and his companions came across it out of nowhere in 1885 Texas.