This is an interesting idea!
How much would and could GDR policies really change, though? Maybe a few churches don't get demolished, maybe the RIAS Trials don't end with death penalties - but on the whole, it would still be very recognisably the dictatorship we know, wouldn't it?
The two most glaring changes would be in the Stasi and the courts. Under Ulbricht and his attack dogs Erich Mielke and Hilde Benjamin both were transformed into something harsher than before:
The MfS under Zaisser and his short-term successor was pretty much a bog-standard secret police: Surveillance of regime opponents, (counter-)espionage, suppression of unrest, arrests for crimes against the people. Generally the victims were then sent to court. The justice system, where opponents were convicted of crimes based on repressive laws and often with forged proof or forced confessions. But again the courts still functioned procedurally like proper courts.
Both of those changed under Mielke/Benjamin. Mielke's Stasi saw repression of opponents in the society as insufficient and ultimately wanted to shape society. This started small with developing the doctrine of Politisch-ideologischer Diversion: The idea that external influences were the primary source of dissent and open repression only adresses the obvious symptoms. From that an increasing turn towards psychological warfare in dealing with dissidents was developed, as well as a need for extensive information about any possible recipient or source of external influences. Other Warsaw pact states to some degree also bought into theories like PiD and strategies like Zersetzung, but never to the same extent. In fact a recurring point of tension between WP security services was that the MfS was seen as too demanding, while the MfS viewed e.g. the Poles as too soft.
Benjamin did a similar reconstruction of the court system. Although to be fair the first steps were done before 1953, when she was only vice president of the Supreme Court (but her decisions there shaped the new legal doctrine): instead of statutory interpretation of the written law (however flawed the process was) its ideological meaning was to be the base of any court decision. And law studies, especially criminal law, were shaped that way: ideological certitude > knowledge of the law > ability to interpret it.
Zaisser, from what we can see today, argued largely for easing some of the restriction and pressure in a classic repressive system and making it more predictable and palatable. Grotewohl otl even after 1953 argued for maintaining rule of law and civil rights as well as more open debates, while still being in support of the SED-controlled GDR. Of them Zaisser seems to be the one more likely to succeed. Grotewohl would likely face a lot of opposition from the party and ultimately Moscow, even if otl they shielded him from SED retribution for his criticism, while the balance between maintaining control and liberal ideals in his ideas seems very unstable.
Either way one further element established by anpower transfer would be a pattern of relatively short terms of supreme control: Grotewohl otl became too ill to work by 1960, Zaisser died in 58 and his closest ally Herrnstad died in 1966.
