You're completely ignoring the core problem here, which is that every weapon that is great versus blobs is also going to be (too) great versus a single unit. Demos were nerfed not because of their effectiveness versus blubs, but because they were a cancer to single units, getting wiped all over the map. Same goes for the Sturmtiger, AVRE, etc.
It simply isn't possible to give a weapon high destructible power to punish blobs without also making them overpowered against single units.
The only thing (imo) that could be done to decrease the effectiveness of blobs is either giving units a Received Accuracy penalty based on how many squads are in close proximity, or to enlarge the effects of Incremental Accuracy on the weapon, so they become noticeably more effective the more squads there are in their firing cone. Only with smart mechanics like this, weapons can be made effective against a blob without making them too powerful in single unit engagements.
But that's something for a CoH3, because CoH2 is too far gone at this point (as in, no more major changes allowed by Relic), it would take a hell of a lot of trying and testing, and I'm not sure if the engine could even support it.
Capping deaths, debuff or max damage to the point that the blob is effectively destroyed with any support but it's not worth it for a single unit as its over kill. Wide AOE that hurts vs medium aoe that wipes is much better and more directed towards combined arms. Could also have a debuff to these blob punishing units that doesn't outright kill but makes blobs less effective for a bit after being shot. It doesn't have to be all or nothing but the units that used to punish blobs ARE nothing now. Can't remember the last time I saw an AVRE, last time I saw a sturmtiger was when I used it and it was awful its more punishing to use than it is for punishing blobs.
What's more, setting up a trap or spending 180+ fuel to wipe a unit every ~2 min hardly seems uneasonable if it means blobbing is also punished. If wiping 1 squad means you can punish blobs id sooner that than allow blobs free reign assuming there is no other option.
Im not a fan at all of punishing mistakes irreparably, but blobbing is not an mistake and if the proper tools are brought to the table they sure as shit should bleed.