Any significant "Greater Finland" scenario needs to be a Russia-screw, and to a smaller extent a Sweden- and Norway-screw (considering the Tornio River valley and Finnmark). I think it is very unlikely to screw Russia/USSR, etc, as hard as to make the maximum Greater Finland mentioned in the OP possible after 1900.
The closest to this, like Baron Bizarre and hwyl say, would be Nazi victory. My rationale for Hitler being as "generous" to Finland as to allow it to take all of East Karelia, Ingria and Kola besides is that the Nazi machine would be so heavily overstretched trying to control European Russia, on top of all other conquests, that it would be a practical necessity for Finns (an Finnic auxiliaries) to police large swathes of the former USSR for the hard pressed "master race".
Even in this case, Estonia would be off the table, as this is "old Germanic land". I have suggested the idea of some of the Estonians being relocated to East Karelia to build an "Estonian homeland" (reservation, really) there while historical Estonia itself is Germanized. This is just my personal conjecture, I don't think there is anything in the actual sources to suggest this would have been planned - it is something that might have suited both German and Finnish interests, that is all.
Needless to say, this sort of Greater Finland is not really in anyone's interest and it would be very unlikely anyway as it hinges on Nazi victory in WWII.
hwyl said:
Another interesting possibility would have been a total occupation by the Soviets - Stalin seemed to have had some plans of reuniting Soviet Karelia with Finland as a new SSR, which would have made any re-independence in the 90's rather interesting. But luckily we escaped that option too...
Agreed. A Finnish SSR would have been bigger than OTL Finland, as it would have included most of the Karelian ASSR, too. But even if the USSR would fall in the end and such a bigger Finland would regain independence, this would still not be preferable to the OTL. It would be a much poorer nation, with a lot of ecological damage all around and a large Russian minority (up to 30-40% of the population, possibly) to boot. This Finland would include some of the Karelian isthmus (with still a large Leningrad hinterland annexed to the Russian SFSR), all of Ladoga Karelia and much of Eastern Karelia. Kola would be off limits, probably, due to strategic and economic reasons.
I have linked this before, but let's do it again -
here is a (rather large) 1939 map depicting what the USSR would have, ostensibly, offered to O.W. Kuusinen's Finnish Democratic Republic during the Winter War. It is an actual OTL map held by the Finnish National Archives. Notice that it would have given Finland most of Eastern Karelia while still leaving Kola and the Murmansk Railway on the Soviet side, as well as removing some land from Finland on the Isthmus.
Never Down said:
I just had the thought, what if the Soviets managed to overpower and conquer Finland, and with a worse breakup then OTL, the Finns manage to leave, taking Kola, Karelia, Ingria, and Estonia with them? Would that be at all possible? Such a state would exclude Finnmark/Northern Sweden, tho.
The problem here is that of these areas, at least Kola, Ingria and Estonia would not have a Finnish majority. A newly independent Finland after a Soviet breakup would do well to avoid claiming majority-Russian areas, especially, as those would definitely cause it problems down the line. And anyway, like I pointed out above, many of the areas you listed would not have been parts of a Finnish SSR anyway as the Russians would not have allowed that on strategic, demographic and nationalist grounds.