The only way to have a successful women's NHL is this: give the women's sport something that the men's sport doesn't have.
What would that something be?
There's one simple solution:
Every game is played outdoors.
Imagine if 15 cities all built special outdoor stadiums just for a new women's league that could hold a couple thousand people. If the sport gained popularity, more seats would be added.
After teams are established, the next step is to let the players vote on whether or not to allow checking. It should be their decision, not anyone else's. If checking is voted in, then after one season of having it, the players would vote on whether or not they want to keep it in the game.
Women's hockey CAN be almost as entertaining as men's hockey at times. When watching the Canada vs US gold medal game in the olympics this year, I was on the edge of my seat. I didn't care that men could beat them, because the players are still the best in the world from their gender. Whether or not men could beat them at hockey is irrelevant.
Make the outdoor rinks about more than just the games. Put some other stuff next to the rinks that you can only access if you have a ticket to the game: some skating rinks for kids, barbecue stands, a warming hut, a sports bar, a restaurant etc etc. I would totally love to go to an outdoor women's game, especially if it was turned into a real event like this.
Make sure the playoff structure is interesting. I swear, one of the reasons why MLS isn't more popular is because of its boring playoff format. A best-of-two series? Are you kidding me? How are you supposed to generate media hype around that? My area's minor league baseball team seems to have more fans care about the regular season than the playoffs. The playoffs are never hyped, and I'm confident it's because the championship round is a boring 2-3 format best-of-five (only the team hosting the last 3 games can actually win it at home, and the home field advantage is determined by whether it's an even or odd year! Seriously, the women's league CAN'T be lazy with its playoff format. A boring playoff format WILL make it harder to create hype around the sport.