@Haimy – you have a conclusion you want to reach, and dismiss anything that would lead elsewhere.
The quote from Rav Chaim Voloziner is his view and is worthy of respect as such, but is not necessarily widely accepted – are there others who say something similar? If so, please do note whom they are. Also, it’s not clear if the second sentence re: not being able to do so today is from Rav Chaim or not – can you please clarify?
One interesting point – many great poskim were also administrators of communal institutions or dealt with the day-to-day lives of their Kehilos, so they had significant knowledge of everyday life. In fact, I was told by one Rav that the reason he Orech HaShlchan was the main Sefer used for Halacha in Europe was that its author was a practicing Rav of a town – so the piskei halacha were grounded in practical experience.
Not all Rabbanim in Europe did not agree with Zionism, though clearly the majority did not do so. In the Sefardic world, there was much less opposition – but it also was much less prevalent. But all of that is besides the point – the Zionism of that time is significantly different from the Zionism of today, and it is unknown how many of the Gedolim of yesteryear would relate to the currently-existing State of Israel. And please, don’t compare Religious Zionism with Meshichist Chabad – Meshichist Chabad is more akin to early Christianity than to Judaism, as they believe in a false Mashiach who will have a second coming. Comparing it to non-Meshichist Chabad is something I’d disagree with, but is more reasonable – I may think it’s wrong, but it is not a Hashkafic issue where they are no longer practicing Yiddishkeit.
With respect to a Milchemes Mitzva – you are too quick to dismiss your potential obligations in such a scenario. Where do you see in the Halachos of a Milchemes Mitzvah that you need an “acceptable army framework” to join such a Milchama??? “Gedolei Torah” do not plan and fight battles any more than they perform surgery – they should be consulted on the Halachic aspects of both war and medicine, but the bottom line is that the experts are the ones who decide on both how to fight and how to operate. It should be noted that one of the key aspects of the newly-forming Chashmonaim Division is specifically that it will have Chareidi poskim for Halachic matters – so there’s that issue addressed.
an Israeli Yid