>> Nice work! Sad, though. I wonder if there's any way to get some of the old Nick back... <<

Well, one obvious step would be to get him away from the corrosive influences.

>> He does seem to be portrayed more sympathetically in Agents of SHIELD, though there's certainly reference to previous mess-ups and manipulations. <<

Also in Captain America 2: The Winter Soldier there were strong hints of some things that fed into his moral devolution: "Things like this are why I have trust issues!"

>> Maybe Phil's been working on him? <<

That's possible.