Seems like Reed here wants an entirely different game.
Honestly, having the entirety of Gettysburg with every unit involved at your command would probably be a total mess. There was a scenario like that in Sid Meier's Gettysburg! but it was a mess to try to keep track of all those regiments. There's a limited amount of attention and time available to a game that purports to be good in MP, and good in chunks smaller than whole evenings.
Also, LOL at the idea that wargames from the 70s and 60s have much to offer. I've seen a lot of them, and they're total dreck. Even the 80s is full of crap. Modern wargames, CDGs, hex and counter wargames, all of them are so much better designed. Guns of Gettysburg is probably the most interesting treatment of the battle i've ever seen in a wargame.