I believe the correct translation is "go out and see how the people act". The Gemora uses this when there are two opinions about an halachic question, such as the correct blessing on water (end of sixth chapter of Berachos), and we want to know which one to follow.

There is another concept that you may be referring to, that the Arizal and other mekubalim find important reasons for Jewish customs that apparently started for unrelated reasons. For example, Jews today wear a small tallis under their garments and a large tallis over the garments. Originally there was only one big tallis, which Jews wore all day. But then they stopped wearing four-cornered cloaks, and in order to fulfill the mitzvah of tzitzis all day it became necessary to wear a special small four-cornered garment. However, the Arizal explains that the small and large tallis each correspond to certain kabbalistic concepts and it is important to wear both. This implies that G-d guided and inspired the Jewish people to begin customs that actually have deep reasons behind them, although they didn't mean it.

There is another concept you may mean that we must be "melamed zechus" on Jews and try to find ways to permit what they're already doing, e.g. the Bach permitting chodosh (Yoreh Deah 293).

However, none of these concepts applies to Zionism. There is no dispute among authorities as to whether it's forbidden, that we should look to the people for a ruling. It is not a Jewish custom started by religious Jews, but a movement started by Jews who had broken away from Torah. And we don't need to be melamed zechus on something if the people doing it were in any case wicked Jews who didn't keep any of the other laws of the Torah. There were gedolim who encouraged settlement and yishuv Eretz Yisroel, but no one permitted Jews to fight for political control of the land.

You are right that Zionism may be part of G-d's plan, but that does not make it right to do it. The Brisker Rav once said that even if prophets and the works of kabbalah predict that there will be a Jewish state before the coming of Moshiach, it is still forbidden to help it happen. He pointed to the famous words of the Rambam (taken out by the censor in standard editions) that Christianity and Islam are part of G-d's plan to pave the way for Moshiach by making the ideas of G-d and the Torah known to the whole world. Does that mean, said the Brisker Rav, that we should go help spread those religions?

One oath prohibits going up as a wall, and another prohibits rebelling against the nations. For those (Maharash Yafeh, Rabbi Yonasan Eybeshutz) who understand that "as a wall" means any mass aliyah, it is clear why these are two separate prohibitions. But according to those (Avnei Nezer) who say "as a wall" means only with a strong hand, i.e. warfare, why did there need to be a separate oath for this? If the Jewish people takes the land by military conquest, isn't that rebelling against the ruling power? The answer is that if there is no ruling power, as in 1948 when the British vacated the land and left the Jews and Arabs to fight over it, then it may be this is not considered rebellion. However, it definitely is considered taking the land by military force.

This is besides the oath against "forcing the end," which means doing on our own actions that are supposed to be left for the time of redemption, like conquering the land and gathering the exiles. This oath has nothing to do with whether the gentiles allow it or not. Even when Mordecai Noah proposed a large Jewish colony on Grand Island in 1826, the rabbis of Europe protested that this was an attempt to end the exile by political means.

In reply to your line about Bar Kochba: Yes, Bar Kochba's revolt was also a violation of the oath, as stated in Midrash Shir Hashirim 2:7. See also the Hirsch Siddur, p. 703. According to the Yerushalmi that Rabbi Akiva held Bar Kochba to be the Moshiach, there would have been no violation of the oath. That is not to be compared to the Zionist movement, which makes no messianic claims. For more details on this see our Parsha Pearls, Tazria Metzora.

The UN can vote to recommend something, but it is not a ruling body. Sometimes it does take steps to enforce its decisions, but in the case of the 1947 partition vote it did nothing. It was nothing more than a recommendation. (Later on, Israel itself flaunted the UN's recommendations many times. Ben Gurion was known to say "Oom, shmoom.") The war of 1947-8 was not a defensive war, but a war to establish something new. Palestinians and Zionists were both living equally in Palestine before the war - why should you call the Zionists the defenders and the Palestinians the attackers? One could just as easily say the opposite. The Torah prohibits a war to take over the land (in our time). The fact that the United states and the UN were behind the Zionists means nothing more than if the UN and the United States would permit Jews to eat pork.

Let me clarify what I said before: Bar Kochba made a claim that he was the Moshiach. Even Rav Kook and the most messianic Zionists (except Lubavitchers) didn't point to any particular person as Moshiach. Read the Parsha Pearls for Tazria and you will see that even claiming that someone is Moshiach is not enough, that messianic candidate has to actually do something to prove himself, either a miracle according to the Raavad or bringing the entire Jewish people to teshuva according to the Rambam. Now, Rav Kook and Mendel Kasher and others attempt to circumvent these problems by saying that the building of Jerusalem and the wars can come before Moshiach appears on the scene. But they fail to deal satisfactorily with the issue of the oaths - how can all these things be done unilaterally by the Jewish people before Moshiach comes, if the oaths are still in effect? We need nothing less than a clear sign from G-d (a miracle or teshuva of the entire people) to know that the oaths are no longer in effect.