The idea of a Central European Soviet Confederation sounds pretty intriguing. I'd like to see someone with the knowledge develop the idea, though it does sound challenging!
Well, for one thing unless the POD was well before WWII and involved homegrown Communist revolutions in the Central European countries, they wouldn't call themselves "Soviet." They might well in the 1930s, but after the war "Soviet" became pretty much a term for USSR institutions only, and the postwar, eventually Warsaw-Pact countries were generally called "People's Republics." Or, as in the case of East Germany, "Democratic Republic." Or even "People's Democratic Republic..." The idea was, since they hadn't pulled off their own revolutions, it was premature to call them "socialist." They were in ideological terms pre-revolutionary, composed of multiple classes, and so not really ready yet for socialism as such; instead the Soviets would help to smooth their transition toward actual socialism and meanwhile recognize a multi-class government. For quite some time, the various eastern bloc republics did maintain alternate parties to their respective Communist ones, which were sometimes not even called "Communist" parties. Of course the leadership and members of these alternate parties quickly learned to understand just what the limits of their permissible opposition were, and eventually it became too inconvenient and dangerous to the regimes to even maintain the facade of loyal opposition, not when it so often proved disloyal!
I'm thinking this refugee bloc caught between the superpowers might well call itself "socialist" in defiance of Moscow's prior judgements, but they probably would not adopt the Russian world "soviet" even to defy Moscow's claim to own the mantle of revolution and post-capitalist democracy. Ironically they might be more likely to have the actual thing itself, in the form of genuine worker's councils given serious discretionary power and substantial freedom to discuss and debate policy.