Well if one argues about overlap between a flame tank and main battle, I have to poin out the diffidences.
Actually I was the one that pointed that OKW and Soviet do not have similar units...
Not it would not but it would make KV-8 less of investment, so less of risk and thus a better choice on certain map.
I do not see how KV-8 overlap with soviet light tanks but even if it would I do not think it would a bad thing especially after reading again and again, how much soviet are depended on the T-70.
On the other hand KV-8 was fine for a long time before it was patched and there is little indication that the proposed changed would cause problems. On the contrary one might actually have more reason to built SU-76 and support his KV-8s
And if we accept that if it become cheaper it will overlap with t-34/76 we have to accept that now it overlaps with KV-1.
My suggestion for hezter (and other specialized units) is to become call-in and thus increase built diversity.
You are self contradicting yourself:
You complained that the KV8 and Hetzer got different treatments, which made sense if OKW and SOV had similar roosters. Now you stress that it was you pointing out that they don't. So why complain that the two flame tanks got positioned differently in different factions?
Flame tanks are mostly chosen on more narrow and urban maps, regardless of their position. It would also make the KV8 a worse choice on slightly more open maps where it still functions at the moment, because some of that armor/health would need to go as well, and TDs are better in open spaces. The unit will still stay map dependent.
If you make it cheaper to more LV level SOV has the choice of two AI specialists. Usually only one of those will be build, therefore they are in competition with each other and this also decreases unit diversity. SU76 is not seen because of lacking synergy, but because SOV has better options at every stage of the game. Otherwise we would see more T70 SU76 combos, but we don't. Even at my rank people understand that you throw a game like that. If you put it closer to T4 vehicles, overlap with the T34 is not as hard as with the T70, but still you get a T34 mostly because you want some form of AI capability, because the tank is quite efficient in that regard.
Regarding you KV1 argument: That is nonsense. You compare a stock vehicle with a doctrinal one that can never be built together with a KV8. You will never have the choice of "do I build a KV8 or a KV1", so unit diversity will not decrease. Yes, both units are beefy, but that's about it.
And what does call in have to do with build diversity? Because you want to make them independent of OKW T1/2?