I think the salary debate is a separate issue. I tend to agree that equity should only apply when the business/business environment are also the same.
As far as it being a worthwhile investment, from extensive experience
I can say with 100% certainty that a lot of little girls aren't interested in watching hockey when it is all boys playing, that they're not connoisseurs who are going to be discouraged by difference in quality of play and that they don't give a rats ____ about hitting or fighting. What draws them in are the goals, the celebrations, a little drama and relatability.
I think in general the NHL is cutting its own throat by failing to do outreach to a broad cross-section of little kids and also presenting a product that is more accessible to young girls and poorer families. They are successfully squeezing every cent out of old people who grew up in the HNIC as religion era but a lot of kids now don't watch hockey, families can't afford to go to NHL games, etc. And compounding it they have way more entertainment alternatives.
If the NHL were to do it, would be a very short season with co-branded teams, lots of comp tickets to girls minor hockey and some half decent promotion. It wouldn't be a money maker but it would be a very successful entry point to fandom for a lot of families that would make them money bigger picture long run.
The NHL should be pumping money into minor hockey partnerships and co-branding more inexpensive products as entry points if it wants to be viable in 50 years.
People have a hard time wrapping their heads around something that is mainstream ever not being that way, but the NHL is on the path to self-strangulation with its efforts to squeeze every buck it can while neglecting poorer people and kids.