If there's a Pershing Doctrine, I hope they have it disable Vehicle Crews and M36's.
Breakthrough Armour Company:
Battle Ready (crews may not exit their vehicles for any reason)
Assault Engineers (make up for disabled crews)
Aerial Recon (P-47 recon plane lingers over an area)
M10 Wolverine (make up for disabled M36)
T26E3 Heavy Tank (the keystone of the commander)
Now look, it's not that I'd be entirely opposed to a Pershing doctrine that disables vehicle crews. The problem is the way you phrased it, in that this hypothetical doctrine has an "ability" which does nothing but disable crews.
If it was something like "Battle Ready: Crews may not exit their vehicles but automatically bail out upon death," or "Battle Ready: Crews may not exit their vehicles but REs are built with vet 2," then I could see it. The Battle Ready you have here isn't even an ability. It does
nothing but hurt the user. These commanders only have five spots, and lots of times the difference between a good or bad commander is how many of those five slots are useful. Many people won't use a commander at all if even one of its abilities is poor.
Nobody is going to pick a commander where one of those very limited five abilities is not only useless, but
actually hurts the user too.
Besides that, although I understand why we absolutely cannot allow the Pershing to have a crew, I'd really be wary of using any commander that disabled vehicle crews, especially with nothing given in return. A major part of good USF play is shuffling your crews around and bailing them out to preserve vet. I often take my M20 crew out as soon as its done, replacing it with REs, and then later on replacing it with a major if I don't have an ambulance. Rifles can also be vetted faster by putting them in vehicles, and whenever I successfully save a vehicle's crew I can use them in combat later. They work great as AT troops, have excellent repair utility, and of course it's useful just having another squad on the field for map presence.
I can remember one match where I had a vehicle crew that went through
three different vehicles. They came in on an AA truck, bailed out of that just in time, then got their hands on a Sherman, bailed out of that when they hit a mine in front of an AT gun, and finally took the helm of a Jackson which they used to take out multiple Tigers. Stories like that are one of the things I really love about CoH, how each battle tells a story (written in the burning carcasses of crashed planes of course), and that's another reason I'd like to avoid the total removal of crews, even just for a single commander.