This whole question is flawed.
WHY ON EARTH WOULD YOU THINK THAT LUBAVITCH IS NOT A CHASSIDUS???
A chassidus is defined as a group of followers of the Besh”t’s derech, who follow and are attached to a Rebbe.
Now, being followers of the Besh”t, that is not even a debate. And followers of a Rebbe? There is no chassidus that follows their rebbes more than Chabad!!
Levush and language, and living all in one NJ village or living in towns and cities all over the world? That’s just ‘by the way’ things. Satmar have their levush, (two types actually) because that’s what their rebbes have taught them. Vizhnitz and Belz build their own chadorim, because that’s what their rebbes want. Ger don’t, and send their children to other chasidus’s chadorim, because that’s what their rebbes taught.
Going back to Neville ChaimBerlin, “Lubavitcher’s use pronunciation like Litvaks, they hold by the Gra’s times, they don’t dress like other Chassidim, they don’t seem to get married as early at other Chassidim, etc.“. They actually pronounce like Russians, as that’s where the chassidus comes from. The Gra’s times happen to be the same as the Alte Rebbe’s. They don’t dress like other chassidim? Well, Ger don’t wear streimels and Belz wear black socks on Shabbos. No one besides Skver wear boots and amshinov klaps hoshanos on shmini atzeres night (or close to it). That doesn’t make them not chassidim. They don’t get married as early as other chassidim because they follow their Rebbes instructions.
What people forget, is that Chabad doesn’t only mean going to live in the back of beyond and giving kosher food to Israeli backpackers. Chabad Torah and machshavah is very deep and profound and the greatest talmidei chachomim learn these works.