WYSIWYG tolerance and sub group units with music flag and chief...

[TheOtherJosh]

Amusingly enough way back in 40k second edition they gave you a “Ork Dreadnought” in the box....

It was a cardboard picture of a dreadnaut with a datacard on the back... and a GW stand.

This is literally what it looked like from the front:

And this was printed on the back ...

[Skabnoze]

@TheOtherJosh And at one point Space Marine Dreadnoughts looked like this:

Note that the base is a 40mm one.  Those guys were not much bigger than the current plastic terminator model.

[TheOtherJosh]

@Skabnoze I think we might be dating ourselves ....

In any case, to the OP, GW has a clarification regarding the command models:

 “Command models must be represented by appropriate Citadel Miniatures if they are included in a unit.” P.238 Core Book

If the models aren’t the designated versions they are, by definition, proxies.

Here’s something to think about that is in the Core Book Designer’s commentary:

”ARMIES
Q: Is it okay to use ‘proxy’ models to stand in for models that I do not have but want to use in a game? For example, using a Slaughterpriest model to represent a Bloodsecrator, or using Stormcast Eternals models painted in the colours of the Hammers of Sigmar to represent Stormcast Eternals from a different warrior chamber?
A: The use of proxy models is generally frowned upon, because doing so can confuse the other players (and sometimes even yourself), and because it spoils the spectacle and aesthetic of the game. Because of this, you can only use proxy models if you’ve gained your opponent’s permission to do so before the game begins.”

As long as a model is an official model, and isn’t outside of the limits on the Warscroll it’s fine to have multiples of Command Models. And per the Core Rules, they can be equipped as they come out of the box, no requirements to remodel for two-handed Weapons (as an example.) per the section on Command Models.

But, like always, have a conversation with your opponent. And make sure you’re all on the same page for any proxy’s that are being used.