AG suspects what Swagger has in mind and is giving him tacit approval?

The AG meeting with most of the characters (still living) was the weakest scene of the film in my opinion. Perhaps the AG is a "Robert Kennedy" like character, in that case he will be removed soon enough crossing too many who hold the real power.

Your idea however may be the intent of the writer after all.

Another thought perhaps Swagger now works for the AG and took out crooked Glover and the f'd up senator, as some sort of angel of death. Although I doubt he'd work for anyone in the government he mistrusts.

I don't think Swagger had what he did in the end in mind during the AG scene. He was going the route of justice via legal/official means to do what he thought was right and bring justice the way he thought it should be done, yet nothing came of it. It probably wasn't until after that scene that he started to consider going the way of taking matters into his own hands. But I think he was really hoping for Glover and the Senator to get arrested or something. In a sense, I think he was trying to "spare" them, perhaps give them a shot at redemption, an opportunity to turn from their ways. But once things didn't go that way, and he sees that that won't happen, he goes it about it his own way.

definitely... and I think between the AGs comments, and the fact that the 'cabal' saw no repercussions, that is when Bob started planning his visit to their Cabin...

as another commenter said, he was planning for justice, but "Wild West" was clearly plan B.

My only regret about the close of the film, is I think they should have made an express time skip of 4-5 months (maybe give Mara a baby bump to reference the end of the book) and it also seems like a special kind of stupid that Glover Beatty, et al would be dumb enough to congregate in a remote location so soon after barely escaping the situation...

I don't think there was any ambiguity at all. Definitely a "wink wink" moment. Also IMHO, a clear implication that if it looked good enough, the AG would close the case quickly.