I've been been googling around about what would happen if the Charlottetown Conference led to a Maritime Confederation/Union. It's not discussed much around here, but I found one thread where someone argued that North Americans really had no say in whether or not they confederate:
https://www.alternatehistory.com/discussion/showthread.php?t=6455. I don't know if that's true. It seems that confederation happened exactly when the residents wanted it to. Someone who knows their history can enlighten me.
Since I'm a bit romantic in my taste of AH, I would like the Maritimes to stay apart from Canada for as long as possible. If they can stick around until the present day, like New Zealand, that's great. But I can see it getting absorbed into Canada in the 1860s like OTL or around 1833 like Newfoundland did. Wishful thinking says that the Maritime Confederation has a republican revolution and never unites with Canada.
I think that if the Maritime Provinces form a federal system, Newfoundland is likely to join soon after, because Newfoundland expressed an interest in the Charlottetown Conference before Canada was invited. I think there would be obstacles to the Maritime Confederation merging with the Province of Canada, because the Maritimers would like their relative freedom, their constitution would not be built for introducing a new giant gorilla province, and their British overlords might be satisfied with the amount of unification that's already there. The Maritimes might join Canada anyway, but it would be that much harder. If they do not merge with Canada, Canada is likely to acquire Rupert's Land and BC. I suppose when they acquire BC, Canada would develop a federal system modeled after their little neighbor to east.
On the other hand, if the Maritime Provinces unite into a single province with a single legislature, I think there is very little to prevent them from becoming a province of the Dominion of Canada in a couple years. I think that this is closer to what was expressed in the original post. Maritimia (pardon the bad name) would be a more influential province than its parts, but it would also be more of a mouthpiece for Nova Scotia. I don't know what affect this would have on Newfoundland.
I know that the original post talked about the Maritimes uniting in the 1840s, and I've been thinking about the 1860s. Off the top of my head, I don't know which one is more likely to a long-lasting Maritime Union.