I was surprised. My imagination really went wild with the ending. Gilbert was high on my list, especially since the letter that he had with him when he was caught at Julia's apartment was written in a completely different voice and style than the other letters. The first thing I thought was that he had written the letter himself and just took it with him to her apartment to cover himself in case he was caught. Another thought was that Gilbert had a need for money to support his morhphine purchases, so perhaps Macauley tried to buy his cooperation by having him write the letter and go to the apartment
I also thought that perhaps Guild and Macauley were in cohoots as well. Guild kept mentioning his silver fox farm in California, and all I could think of was that Wynant (being the silver fox) and Macauley had setup the whole scene as a means of escape from the Communists that the Aunt Alice mentioned. Perhaps when Macauley went with Guild to Pennsylvania to check out the suicide that Macauley offered up some bribe money to Guild to go along with it.
There is also the Halsey(ghoul/archeaologist/hatchet collector looking to purchase property in PA) and Leda(Tip)(gnome) Edge, Larry Crawley(press agent), Alice Quinn(red head in green pyjamas out for $$), Harrison Quinn (pudgy stock broker with lots of insider information), Margot Innes(?), Phil Thames (Professor at Columbia) group. Halsey described himself as a ghoul. I recently thumbed through a new book about the FBI (sorry I do not remember the name) that had a list of code words used over the years by agents. One of the code words was "ghoul", which was described as someone who finds names of deceased individuals to use as cover names criminals and agents. Larry Crowley gave Nick the Little Blue Book (socialist/communist publication), so does this inclination project to the whole group

Anyway Larry says he sees Victor Christian Rosewater Jorgensen coming out of a hock shop on the day Jorgensen supposedly left NY. Was Larry tailing Jorgensen for some reason or giving him an alibi
By the way there really was a Victor Rosewater that was alive during the 30's, but I do not see the relation to the story.
There were just so many possibilities. In my mind it is possible that Macauley did play a significant role, but I have serious doubts as to whether he acted alone. I think he may have been the scapegoat for a much larger scheme that could have involved everything from the Occult (Freemasonry and others), business (his inventions could have changed the status quo), money(everybody wanted it), and national security(what was the secret betrayed?). My thoughts about this came mostly from my reading on Nikola Tesla inventor (1856-1943). It seemed to me that Nikola Tesla had similarities to the Clyde Wynant character along with interesting tie ins (list from info gleaned from Wikipedia)
-Nicholas Tesla had reportedly suffered a nervous breakdown in 1888
-he was celibate
-had a labs in New York and in Colorado(Packer story tie in)
- fought long battles regarding patents and his inventions
-it was also said that he had an obsession with the number 3 (notice how many 32s and 33s and 3s are in the story)
-disliked overweight people to the point he fired an employee over it. (fat man's clothest in grave)
-During his 1888 neverous breakdown he cut off all relations with family and friends and to the point that they thought he had downed and was no longer alive.
-at his death his papers were seized by the FBI and declared Top Secret.
Nick Charles lived at the Normandy - maybe a tie in to the subject of the article below which is of course only partial)New York Herald Tribune, June 5, 1935
Scoffs at Normandy’s "Speed"
Sees Success for His Plan to Use Stratosphere Ray
Would Light Sea at Night
Says French Liner's System Copied His in U. S. Boats
Dr. Nikola Tesla, scientist and seer whose discoveries in the fields of polyphase electrical current and wireless place him in the front rank of modern inventors, refused yesterday to be awed by the record speed achievement of the French liner
Normandy in crossing the Atlantic in 4 days 11 hours 42 minutes and predicted that enormous ships would cross the ocean at far greater speeds by means of a high-tension current projected from power plants on shore to vessels at sea through the upper reaches of the atmosphere.
Dr. Tesla, a tall, slender man with straight silvery hair, lean features and bright blue eyes that belie his seventy-eight years, prefaced his prophecies by pointing out that the Normandy’s system of power generation and application was not new--but one which had been adopted long ago in some of the United States cruisers. The principle is one of his own inventions.
"In view of the adoption on such a large scale of these inventions of mine, it is interesting to recall that I was violently attacked only a few years ago by a professor of marine engineering at Columbia, who claimed the electrical drive was not feasible and that it was folly to undertake it.
"However splendid the machinery on the Normandy might be, the time is not distant when we will have much simpler and better means of propulsion."
My point about how inventions could turn business interests upside down came from this article (partial)The World Sunday Magazine — March 8, 1896
A Way to Harness Free Electric Currents Discovered by Nikola Tesla
The World is on the eve of an astounding revelation. The conditions under which we exist will be changed. The end has come to telegraph and telephone monopolies with a crash. Incidentally, all the other monopolies that depend on power of any kind will come to a sudden stop. The earth currents of electricity are to be harnessed. Nature supplies them free of charge. The cost of power and light and heat will be practically nothing.
I could go on, but I think Hammett was trying to point the way to certain things happening at that time by use of names of his characters. The names were not a direct correlation, but could send someone thinking about issues that maybe he was trying to point out. Of course the names would be more meaningful to readers of the day who understood the times and would more easily recognize the character names.