I seriously doubt a coalition like that would ever be a possibility. D66-GL-PvdA-SP-CDA would be more likely (but still very unlikely). We probably would get a centrist coalition led by the VVD in this case. Maybe even VVD-D66-GL-CDA (the one we might get irl, but the coalition in this timeline would be more left-wing since GL won more seats here than irl).
But I love this timeline
Thanks! I was trying to see if its possible to avoid a GreenRight scenario, but I'll definitely take one of your suggestions as the final government (once the one IRL is formed.)
I was just thinking, would ChristeUnie's economically progressive positions ever get it to enter in a centre-left coalition? And, a D66-GL-PvdA-SP-CU would have 73 - which party would be best suited to provide those last 3 seats? DENK? I'm obviously not that well versed in Dutch politics
Nobody wants to work with DENK, they're as toxic as the PVV among most mainstream parties. CU isn't that left-wing on economic issues anymore, I'd say they are pretty centrist on economics but they wouldn't have much problems with joining a centre-left government. They would demand a block on progressive legislation on issues like abortion and euthanasia though, and I don't think D66 wants that. That's the main reason we might not get a VVD-CDA-D66-CU government irl even though I thought it was the obvious choice.
I'm not sure who could provide the last 3 seats. 50+ said they won't join a coalition unless the retirement age was lowered to 65 (extremely unrealistic even with a global left-wing comeback) and PvdD says influence is more important than power (they would rather shift the overton window than join a cabinet). And you also have to take the senate into account. The last senate elections were in March 2015 so I don't think they are different in this timeline. VVD-CDA-PVV-SGP have 36 out of 75 seats in the senate, so it becomes very hard to form a coalition without any of these parties, basically every other party would have to team up. And the PvdA still suffered the biggest loss in Dutch parliamentary history in this timeline so I'm not sure whether they want to be part of a government again.
In the end I still think we would end up with a GreenRight cabinet after months of gridlock (though it would be significantly to the left of the GreenRight we might get irl because VVD/CDA have much less leverage). If you really want a progressive cabinet I think D66-GL-PvdA-SP-CDA is the best option. Klaver and Roemer actually pushed for it irl, but nobody really wanted it. It would be suicide for the CDA, but it might be possible if Buma's right-wing campaign is blamed for the terrible result and he is replaced by someone from the left of the CDA. Maybe VVD-D66-GL-PvdA with outside support from some other parties (in the senate) is an option, but I don't think anyone really wants a government without a majority in the senate anymore.
Maybe you could have a GreenRight coalition in which someone from D66 is the PM? GL and D66 combined have more seats than VVD and CDA combined and it happened a few times in the 60s and 70s that someone from a small party became PM. The VVD probably would refuse it, but if the country really is that tired of Rutte in this TL they might not have another choice. I don't think it's very likely though, I think the 2 options I named earlier are much more likely.