The trouble is that, even with the limitations in your last sentence, there can be several different "stable frameworks" and the ability to capture market share depends on them (the fitness of competitors is determined by the environment). Things like the financial framework, approval, zoning laws. But I'm sure you have been told this already.

prematurely closing current ones is folly

The reason for the premature closures is of course not economic but that the plants had safety issues and operators like Vattenfall cannot be trusted. Then again, there would be an economic dimension if the old plants were required to implement retrofits according to the newest standards (with the protective hull being the main cost factor).

That said, I don't disagree that the precise implementation of the Merkel II government's nuclear phaseout is not reasonable. In a proper planned transition, the phaseout part should be continuous and not big steps, the advertised replacement should not be throttled, other "replacement" should be throttled even if it hurts big business, and grid development should have been pushed more energetically from the start.

_{*Lunatic*, n.
One whose delusions are out of fashion.}