If the boundaries are based on mentality of the citizens, then basically it would be Toronto becoming it's own province, the rest of Southern Ontario another province, and Northern Ontario being the third Province.
Interesting statement. I wonder if the hierarchy would be Toronto at the top and Northern Ontario at the bottom or the other way 'round. Either way, it seems, the Rest of Southern Ontario is in the middle of the mentality scale.
Always an interesting concept for discussion. It seems that the boundaries of any such theoretical new province is pretty elastic, depending on the perspective of the poster (nobody seems to have discussed whether The Suburbs should be in or out, because it seems that some city core folks figure that their counterparts in Scarborough, North York and Etobicoke are of a different world).
There is probably no doubt that Toronto/GTA/GTHA/GGHA needs a new relationship with the Rest of Ontario, perhaps some sort of city charter or something similar. But a new province or even something that looks-like-a-province-but-not-called-a-province is likely a non-starter without a Constitutional amendment, and we all know how much luck we have had with those.
The division of powers between the provinces and the federal governments to do stuff and the authority to raise money to do them is laid out in constitutional law. How much of what is ascribed to the provinces, either expressed or implied, and how much could be further devolved to a municipality would keep legal nerds up for many nights. The argument of any division of Ontario's debt and assets is an interesting one.
Some suggest that this new province could perhaps assume some roles and leave others with the remaining Ontario, such as health care or education. That type of cherry picking would, in those areas, seem to leave the new Province of Megalopolis still in the 'child of the province' situation that it wants out of, with little or no policy or financial control over those areas since they would be little more than a contracted client. I'm reminded of the Brexit negotiations, where the UK seems to want to be out of the club yet retain many of the benefits of being in, while the other side is taking the position that out is out.