Why create a new community that's a directory of other communities? I would imagine that if someone is wondering "Is there a community for my specific city/town/area?" then they probably would either:

• Search the local community list of the instance
• Go to a community that seems to correlate to their catchment area (in your example, c/Ontario) and look there for a nested community that's more local

All told, IMHO the way to improve discoverability of regionalized communities is via making them more visible via the province-wide communities. After all, you found Ontario communities by coming to this Canadian-specific instance first, right?