I've seen a few people say Toronto could support a team as its Canada's largest hockey market. While that may be true, look at the abundance of other, higher quality hockey you can watch here. Two ahl teams very close by, junior teams. Heck, Brampton couldn't support their junior team and Mississauga's attendance is poor and that's better hockey. What makes anyone think people would go to women's games with all the other options?
Toronto already has a team in the Canadian Women's Hockey League called the Toronto Furies, which incidentally is supported by the Leafs. However, the fact you didn't know about it further illustrates your point.
I noticed that some posters are pointing to the CJHL and its member leagues as a point to illustrate support. The fact is the CWHL is essentially that model and it draws flies. The only way the CWHL were to go pro is to follow the WNBA model and be owned by NHL teams and play in the off-season. If the CWHL were to have the NHL fully onboard and with it their sponsors and TV clout (in Canada at least), it might make a go. Considering that minor league baseball and to an extent minor league hockey survive on this model, it could fly.
Quite honestly, the best way to run a league like this is to keep it out of NHL cities (except perhaps Ottawa where women's hockey seems to do well with international teams) and put teams in places where they will be big fish in a small pond. Perhaps look at CHL cities like Saskatoon, Kelowna, Red Deer, London, Halifax etc. look at places that lack NHL teams, but where minor league sports has flourished in the past. That would be your key for franchises, if tickets were in the CHL price point, I could see the CWHL (WNHL whatever you want to call it) do well in the summer.
Frankly, I've often thought a men's summer league in CHL cities would do well. Baseball and basketball have leagues that run in the offseason and do well. I see no reason why a May to August league couldn't work for non-NHL players. So if a women's league were in this timeframe, I could see TV coverage as really TSN and Sportsnet have little to cover beyond MLB and car racing through this time period (yes they have some of the NHL playoffs in May, but there is always TSN2 or SNet 360). But playing in the winter is not going to work as there is too much going on for another hockey league to survive.