Milhouse: The difference you describe between a corporation and a private person doing business, from an exclusively halachic perspective, doesn’t necessitate a corporation. An individual doing business as a sole proprietor can also halachicly effect the same full sale to a non-Jew of his sole proprietorship business, customer list, place of business and all.
As far as dina d’maclchisa are you implying that, say, a yerusha would be governed by New York State law rather than hilchos yerusha in Shulchan Aruch? Or if two Yidden have a financial dispute in Beis Din the Dayanim will pull out New York State law books and rule in accordance with secular law even though Halacha and Shulchan Aruch clearly describe the particular dispute these two Jews are having and clearly rules one way — which is the opposite of secular law? Or that if someone damages anothers property they amount due and even whether he’s liable for anything is determined by gentile laws rather than based on how Halacha says?
Your “tzibur of one” description doesn’t shtim. And, yes, I would certainly say that if a second person joins a tzibur, the tzibur property doesn’t remain belonging to the last person standing prior to the new member even if he was the only member for a period of time. Even while he was the sole member I don’t believe he could disburse of tzibur property for personal benefit.