What would Herzl and Hannah Arendt have to say about the settlements if they were alive today?
A key principal for Herzl's movement was that Jewish immigration had to be "secured by public law". Zionism was not a pirate movement, seeking to occupy land, but one that worked with the authorities both local and international and sought formal approval for its actions. All land was legally purchased and Ottoman approval was sought for migration. The movement focused on winning international approval and its leaders were democratically elected. This policy paid off, first with the Balfour Declaration and later with the League of Nation's creation of the Mandate for Palestine. Would Herzl have approved of the West Bank settlements? I would guess that he wouldn't: the settlements are not supported by international law, there is a great deal of dubious land seizure and they are contrary to the democratic principals on which Herzl built the Zionist movement. Having said that, the sovereign power in the West Bank is the state of Israel, which supports most settlements (although some are built without permisison by "wild cat" groups), so in that respect they are at least partially secured by public law.
Although Arendt flirted with Zionism and was Jewish, she opposed nationalism and was no Zionist. Arendt was highly critical of Jewish authorities behaviour during the Holocaust:
"Wherever Jews lived, there were recognized Jewish leaders, and this
leadership, almost without exception, cooperated in one way or another, for
one reason or another, with the Nazis. The whole truth was that if the Jewish
people had been really unorganized and leaderless, there would have been
chaos and plenty of misery but the total number of victims would hardly
have been between four and half and six million people".
Arendt may be wrong in what she says, and insensitive to the limited choices faced by Jews during this period, but there is a similarity between saying that settlements "must be secured by public law" and trying to work with the Nazis. In a sense what she describes is no different from the policies encouraged by Herzl, and which ultimately won the Jews a state. By the way, most Jewish leaders were arbitrarily appointed by the Nazis and none were known Zionists. Some may have helped save Jews.
The thing is that the settlers, by ignoring the international community and the Israeli state, are working in accordance with the principals Arendt seems to be advising. So in that sense, Arendt's thinking is closer to settler groups then to liberal-Zionism. In the end, the Jews in Nazi Europe were caught in a damned if you do and damned if you don't situation and Arendt's criticism is not the product of a detailed analysis.