The problem with any hypothetical scenario involving a revival of the Soviet economy in the 1980s is that one of the decisive factors in the downfall of the Soviet economy was not caused from within and could not, no matter what, be remedied by internal Soviet reforms. This being the drop in oil prices. Ronald Reagan, as president, befriended the Saudis enough that he could convince them to drop the price of oil exported from Saudi Arabia, and as anyone who's ever studied economics, even on a minute scale (why did the mom and pop bookstore go out of business when the big chain moved in across the street, etc.) knows, that will (and did) cause a worldwide drop in oil prices of around 75%. Since much of the USSR's exports at the time were composed of Siberian and Caspian oil, this caused a massive drop in profits made from Soviet exports to the world market and, over the course of the 1980s, helped in a major way with the decline of the Soviet economy.
However, this cannot be effectively modeled in HOI2. It could be in Victoria, where prices of commodities actually have an effect on the game, but in HOI2 the best way to model it would be to drastically lower the ratio of oil to other goods, which determines how much countries are willing to trade for goods (I believe by default it is 1 energy:2 metal:4 oil:8 rares:16? supplies:32? money) and devalue oil. However, since I don't know if even this would work, especially since the USSR is self-sufficient in many other respects in HOI2 terms, any alternate history created would have to involve not only the Soviet Union but also would have to involve a change in American diplomatic and economic foreign policy, and leave out the bit about devaluing oil.
Not impossible to write, but it basically makes the whole thing into a global alternate history, not just a 'what if the USSR cracked down on the revolts in Eastern Europe'.