A PCI lead Coalition and a Mitterrand/PCF coalition would probably cause Germany to just drop trying to impose any kind of Common Program. Also if France and Italy are working together you’d probably see Portugal and Spain following suite due to there own reasonably successful Communist Parties in the 70s/80s.
You could flip Europe on its head and have European efforts reverse to help solidify the Eurocommunist program maybe.
On the other hand, Mitterrand was never going to be satisfied until he ruled alone so that one sounds shaky. If the PCF avoided some of its decline and they're still holding their own, trying to backstab them may not go his way though, so that could be interesting.
Maybe a reverse of what happened OTL with him still trying to push towards the economic center but not being strong enough to pull it off without looking like he'd enter a coalition with the center right, which would be a step too far for the left wing voters the PS was making gains with. At the same time, he misses the flip going on in Europe so the move ends up looking dumb, the PCF has a clear culprit for the end of the common programme and the PS comes back into the coalition as the lesser partner after a change of leader?
That’s a good idea there, also mean that the PS most likely heads in a Rightward direction whilst the PCF becomes as you mentioned an alliance of Workers/Social Reformers.
The PS could go back to "third force", trying to build a neither Gaullist nor Communist coalition along with the center and center right.
I could see elements of the Labour Left/What would be the Kinnockite strain supporting EuroCommunism methods. One way to ensure British EuroCommunism is if the Green Party violently splintered in the early 80s whilst the CPGB was changing it’s direction. So the CPGB gains the Green Left support that flocked to the Green Party otl and survives (though they’d probably change the party name or something).
Yeah but I still can't see the CPGB amounting to much even then, unless Labour splinters. Which is another way this could go? The Labour right splits strongly, maybe over a Labour left win and popular front attempt, which ends up backfiring because Labour retains the unions.
I think at this point it's worth considering the US is shitting its pants because it has never been able to tell the difference between anything on the left. The CIA might try its hand at some underhanded stuff, and exposing it in the act would also be one way to have a rally around the flag effect for an Eurocommunist party.