Good question. By my previous logic, a State could ban a religion. This would be subject to the State's constitution and its citizens' will. A thorny situation indeed.
...Or make private ownership of guns illegal? Since the BoR was ruled not to restrict the states that would follow.
No. "To keep and bear arms" is a specified right of the People. No unit of government can legally infringe on that right. Only the People can relinquish that right through the amendment process or a constitutional convention.
These are theoretical questions for the most part since state constitutions address these issues. But interesting nevertheless.
Yes. And it's great they are being pondered. For too long the People have allowed politicians and lawyers to perpetuate the myth that they control the Constitution. It belongs to the People. And "We, The People" need to assert our sovereignty is this matter.
Massive public discussion of Constitutional limits placed on government and detailing government abuses of the Constitution are the People's warning shots across the bow of an increasingly out of control government.
States certainly prevented blacks from owning guns until that little squabble of 1861-5 was settled prior to that they were believed to be able to do this.
I understand your argument that the First amendment initially was applied only to the fedgov and that the words "Congress shall..." made it different from the other amendments. But that does not appear to be the common understanding of the Courts. Those which found the 14th changed all that were conservative courts too.