True, John Armstrong designed the GG&N. But remember what Atlas was commissioning him to do - design relatively simple- and inexpensive-to-build layouts that put Atlas products in their best setting. These layouts were designed in the late '50s and early '60s, when massive amounts of RTR locomotives and rolling stock were not available. Outfitting your entire fleet with couplers that both coupled and uncoupled consistently was beyond the reach and ability of most beginning modelers. DC block control wiring and reversing loops were difficult for many MRs to understand. And unless they belonged to a club, magazines and books were the only source material for learning how to do things. There was also no computer software to use as a check for clearances, errors in fitting, etc. That's why Atlas had most of these layouts at least partially built - to check for these errors.
To keep things simple, the GG&N was specifically designed not to have reversing loops. Although it looks like it does, there aren't any as drawn. The modifications suggested by Evan in Armstrong's Track Planning for Realistic Operations do add reversing loops. The GG&N was also required to feature Atlas bridges, Atlas track, and Atlas wiring products. When the layout was designed, wiring products such as Atlas were the norm, as were central control panels. Atlas Controllers, Selectors, Connectors, and switch controllers do NOT support walk-around control, nor are they very useful with large numbers of blocks or turnouts. The reason for the latter is the gang mounting so that you have to memorize which electrical switch controls which block or turnout, or at the very least refer to numbers and letters on a track diagram. All of these factors make switching operations relatively difficult, and favor "spectator" type track plans. I know from having built 2 Atlas layout designs in HO - Simplicity and Great Plains, and an expanded Grand Trunk Western - as a teenager with my Dad.
Furthermore, most MRs in the '50s and '60s came from tinplate - Lionel and American Flyer - backgrounds. Tinplate is designed for spectator operation. Slow speed operation and switching does not come naturally in the tinplate world, and is usually quite frustrating unless equipment modifications are made.
To make switching fun, you really need local control of train and turnouts, combined with decent sight lines for coupling and uncoupling. You also need reliable couplers that permit pushing without derailing, and a reliable uncoupling system. And finally, you need locomotives that perform well at switching speeds. Putting all these considerations together was rare before the late '60s, and so many (but certainly not all) layout designs from before then tend to minimize switching.
That said, I have modified many plans from that era that I do like to make them more operationally satisfying from an "engineer" perspective. I personally don't care for operating "dispatcher" style - I have to do too much teamwork on the job. I prefer my MRing solo or with 1 good friend.
In fact, my ultimate plan puts together modifications of the Portage Hill yard from the PH&C of MR 1962-1963, the Sierra Pintada from MR 1966, the Gum Stump & Snowshoe (MR Sept '63 and Apr '66), and the Tidewater Central from MR Dec '56.
my thoughts, your choices