Saying the rambaN doesn’t “hold” of the shvuos is only possible if you don’t read his maamar al hageulah where he QUOTES it beferush!
The kasha on him vis a vis how he could hold of a chiyuv to live in EY while there’s a prohibition on going there en masse is dealt with extensively in the poskim. It’s not that big of a deal. The simple answer is that everyone should try, but Hashem will prevent some people and it won’t end up being en masse.
The balfour declaration (and even the UN partition plan) are irrelevant because when the zionists took over, the british were no longer baalei batim on the land. Their permission is just as valid as China’s; same with the UN – it doesn’t matter what most goyim say, if there is opposition (as in, the independence war with a bunch of Arab armies) then you do NOT have permission to go en masse.
Making a state is a separate issue; rav meir simcha never spoke of it, rather the issue was mass immigration. Declaring a state involves another shvuah, of not forcing a geulah; on that I don’t believe having permission helps.