I would say that it would be easier to keep the GTA and the western part of the Golden Horseshoe as Ontario and split of rest as separate provinces. West of the new (smaller) province of Ontario, you'd have Hurona with the capital at London. Split the area north of the new province (of Ontario) along the same line as the southern boundary of Quebec. The southern part could be called North Ontario (just to be cheeky) with the capital at Kingston. The northern part (that contains Ottawa) would end somewhere north of Petawawa and south of North Bay (not sure what to call it, maybe Ottawa, after the river, just for shits and giggles so that we'd have Ottawa, Ottawa
). That would leave the whole north part of the current Province of Ontario as another province, capital at Sudbury (or Thunder Bay, maybe).
None of this will ever happen, of course, but I think that Ontario and Quebec are way too large and need to be split up into smaller provinces/territories just to balance things out in this country as a whole.