Just like RoadRaven said, it's not the assembly of the mag that's the big challenge - it's attracting advertisers. You have to have an awesome marketing person who can find and keep advertisers who want to sell specifically to women, and it's not a big field out there, unfortunately. My sister-in-law started a mag called Dandelion (dandelionmag.com) that is dedicated to women in the outdoors (all sports) and it's pretty tough to 1) find startup funding and 2) keep advertisers interested in investing. So, if anybody has marketing experience.... I would LOVE to subscribe to a women's cycling mag!!

Articles on where to locate cute women's apparel
Bike fit for women with "body type" guidelines
Where to bike - safety issues
Interviews with women pros and how they got started
Encouragement for beginners
Success stories of "average janes"
Tips from folks like Irulan, who make bike clothing
Tips from mechanics
Recipes for on-road nutrition (Corsair, where are you?)
Special issues, like allergies, injuries, etc.
More articles that address the "spiritual" aspect of cycling, like this forum does!