To add a grain of salt into all that:
WI there would be a domestic political crisis in West Germany between 1987 and 1989 that led to premature Bundestag elections, leading to an SPD-lead government under Oskar Lafontaine at said 11/9/89? Lafontaine was fiercly reluctant to a quick reunification and demanded to exempt East Germans from the West German welfare state to keep it from breaking down.
I think this would be a reasonable enough POD to serve the purpose.
Yes, exactly, if you want to delay unification--conceivably, defer it indefinitely--in the immediate context of 1991, you need to look at reasons why
West Germans would delay it. OTL there was a lot of grumbling at the time and after amid all the euphoria.
The Soviets were withdrawing and collapsing, they can't restore their old regime if they try, and trying would be a sure way to kill it. The East German Communist establishment had no legs to stand on without the Russians.
Later East Germans would realize the West-dominated Greater Germany was not the earthly paradise they dreamed of, certainly not for them, but at the time the thing was to get away from the DDR, by leaving it or definitively abolishing it.
If the East Germans had no where to go, I am sure they'd have repudiated their old regime anyway and would probably have lobbied the Western states shamelessly for some kind of acceptance into Western Europe on some basis--the Common Market; NATO--anything.
Also they'd want aid--loans if not grants. Can they get it from anyone but West Germany?
In those circumstances, could West German politics, parliamentary shifts or not, still keep from reabsorbing the East immediately?
If they could--then I can see the Easterners changing their minds about their rush to get absorbed and carrying on as a separate state, even if later West Germany changes its tune.
What if the GHW Bush administration sees propping up East Germany as an even surer bastion against future Russian ambitions than the West, and is forthcoming with aid and reform advice seriously meant to put the former DDR (what would it be called now? Simply
Ostdeutchsland?) on its feet among Western nations? Would West Germans resent that or would they welcome being spared the headaches? And how big a bill for the US taxpayer are we talking about--bearing in mind the USA and whole capitalist world was spinning into yet another of our recessions that come every damn decade like clockwork?