Profile of Hannibal

This is just pure nitpicking if you ask me. We can as well say, why "War Machine" existed in vCoH, because it also does look kinda fictional. I will repeat myself again, lets just sum up what kind of fiction was allowed for CoH across both games:

1) Misrepresentation of units
2) Some fictional abilities on units
3) Rare or super rare used equipment representation
4) Believable abilities made to fit gameplay
5) Fictional, but belivable, ammunition on a small scale (grenades mostly)
6) Pure gameplay abilities which-in the scope of represented factions (vCoH USA "War Machine")
7) Wrong time periods
8) Wrong availability of rare equipment

Where would you put Black Prince? It wasn't finished, it wasn't used, it wasn't put into a production. Literally 6 were made and all 6 were prototypes. Besides the fact that BP looks like a ww2 tank, it doesn't fit into any category CoH previously allowed itself to mess with.

The BP does not fit any of your bullet points, but the problem with your list is that there is no reason for it to be the "be all end all". Why should there not be a 9th point added to it? The criterium is not 'what has been done before', but 'what is authentic'. And that's obviously a very subjective criterium, as we can see in this discussion. Some players basically don't care at all, some are very specific, and everything in between.
The BP is a vehicle developed for the war, based on a vehicle and components that have already been used in the war, but the BP itself has never been used in it. We can therefore make some estimates how it might have performed in battle, but using it in a CoH game is pure fiction. My point is, that there is no >huge< difference to e.g. the V1 rocket in CoH: This weapon, as portrayed in the game, has not existed and it is pure fiction. Just pretending it were a "V1 rocket" does not make its use authentic. There has never been a rocket of this type in WW2 that could even somewhat precisely strike a battlefield. It does not get any of the characteristics of the V1 correctly. It looks like a V1, and the name says V1. That's about all there is. Which leads me to the next point, which you summed up perfectly here:

And it would have been perfectly fine with-in the scope of how CoH gameplay mechanics works. Aside from balance\faction reasoning and some commons sense, kubelwagen could be made into a TD, with an ability to fire its MG into some tank weakspot or something

Stuff like this we have already seen in CoH1 and 2. Authenticity is not a binary decision, it's a spectrum. At which point something looks out of place is a subjective thing. Is the BP okay because it looks like a WW2 tank and its performance can somewhat be estimated, although it has only been prototyped? Is the V1 rocket okay, since it is a weapon that has been used, albeit nothing like portrayed in the game? Is the Sturmtiger okay, although it is a rare vehicle and actually had more the range of a Katyusha than a tank?
How closely the in-game unit has to resemble the real thing is really personal taste.

As I stated previously, I'd personally rather not have the BP in the game for various reasons. But it also won't completely break immersion for me if Relic keeps it. I can live with it, but I also don't get why Relic clings on to the BP so much.

Better, but still looks untidy to me.
So many floating and protruding elements, why? CoH2's UI occupies way too much of the screen, but at the very least it is thematic and clearly separates the screen into the battlefield and static elements.
CoH3's UI is not thematic at all and constantly mixes static elements with snippets of the moving background. E.g. near the minimap. I don't need these tiny spaces to the left and bottom, I won't pick up information through these anyway. This could at least be used to make the UI 'pretty' or but some better info there.

Well now it's definitely not worth it to be in 2CP it is, in the current situation it's only suitable as 0CP or as British Assault Section. I'm afraid it won't change anyway. Are patches planned at all? Or just wait for СoH3?

Not that I'd be any official, but there is nothing planned for CoH2 anymore. Would be highly strange behaviour to divert attention to the previous entry when the next iteration is coming out in 2 months (and obviously still needs a lot of work).

2CP timing is like ~6-7 minutes. Not hugely mistimed in my opinion. The timing of the upgrade also has nothing to do if they should be come almost an elite unit or not. Current Conscripts get their 7 men upgrade even later, this doesn't mean they should out-do all other infantry on the field including elites.
6-7 minutes is fairly normal for weapon upgrades to come unlock.

If there ever were a patch, there's two options: Either - as you suggested - remake them into a specialized call-in like squad or 0 CP upgrade, or keep the current timing and design with adjustments to make it really worth picking over the 7 men upgrade.

I've pointed this out to you before, we require at least a minimum effort for opening posts in balance threads.

I'll lock this thread since there is no point to it this way.

I wouldn't chose to say Elefant mass produced either.

You are simply wrong.
Elefant was the most successful mass produced TD in kill ratio with around 10:1 score.

Which one?

Point here is that Elafant had probably the best kill ratio (around 10) (for TDs that went beyond prototype).

The 12.8 cm Selbstfahrlafette auf VK3001(H) seems to have had a better kill ratio of above 11 but was only build as prototype and only 2 where ever build.

I am not sure why some people choose to argue semantics about mass production when the point was the actual great record Elefant achieved and not weather it was mass produced or not.

That's also not the point.

This part of the discussion originated from the question if and to which extend rare vehicles should be represented in the game as an extension of the whole discussion around the Black Prince. Since CoH allegedly aims to be authentic, the battles it shows and units within them must be authentic too. All of this was basically embedded if unicorn units should be in CoH3 because the weird designs obviously kick the door open for interesting mechanics and unit designs, or if CoH3 should rather stick to the most prevalent vehicles since it is not very believable that in the specific skirmish that you fight, a huge portion of very rare vehicles will take part and duel each other.

A prime example of this for me would actually be the Ostwind, I am amazed that no one mentioned it so far. The FlakpanzerIV was a late development as well. However, Relic not only decided to make it a stock option for Ostheer, but also chose the Ostwind, which was the least numerous of all Flakpanzers. They could have taken at least the Mobelwagen for that purpose. They didn't, and yet, no one seems to complain about it in this discussion. It slightly feels like people would just randomly pick what they care about and then press through all of it.

In my opinion: As long as a vehicle has been used in WW2, they can take it. "Rarer" vehicles should be bound to doctrines so that you don't see more of them in a single battle than have been built in the first place. But they can add a lot of different strategies to the game, because let's face it: If you strip away all the details that a CoH game cannot represent, many of the most produced tanks over the course of the war just fall into the same category with different flavors of "strong".