Last thing I heard was you only get to say that a company should contain, say, "medium tanks", and the game will just pull some from your pool, with you having no say as to what types. Which kinda ruins some of the fun of creating tank variants. For example (just an example, don't nitpick this), I might want to create an especially fast and reliable Panzer IV variant to put in a kind of "overrun/encirclement" division template, and well-armed and well-armoured infantry tanks to put in an infantry division template, where lack of speed won't be a hindrance.
If we do get to choose somehow, that's great news. Otherwise, I'm hoping it will be something that makes an appearance in a patch or mod. War in the East has these fixed "a rose is a rose is a rose" approach to divisions, too (every infantry division has the same T.O.E and thus the same units), but it still allows you to attach stuff to the divisions. For example, I might give an infantry division a Stug battalion for its assault on a Russian fort.
I know the division template system seems a bit "rigid", but at least letting us choose which divisions/templates get which variants should be one of the things allowed by the game. Those who don't want to micro can just let the game assign tanks and whatnot for them

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Giving
individual divisions attachments could actually be possible in HOI4, too, if you just substract some vehicles from the player's pool and give the division an appropriate "has attachment" modifier. Like "Assault gun battalion: +5% fort attack".