That’s easy, Lube: cuter uniforms. Actually, in the soccer world they’re known as “kits”, which is a much cuter word than uniforms, so you’ve already got a leg up there. Kit is like a shortened version of “kitty,” and as a quick Google image search for that term will reveal, everybody loves kitty. I think I may have even seen that on a T-shirt.
I am also going to recommend you look into something with fringe or sequins or tulle - ideally in a color that really pops - maybe a chartreuse or a vermillion or an aureolin. Never heard of those colors? Of course not. Otherwise, you wouldn’t be asking me how to attract female players. In fact, you might not even have a desire for women players at all.
The right fabric is important, too. No self-respecting female would be caught dead wearing 100% polyester - not even “breathable” polyester (which, by the way, doesn’t exist - just like unicorns, leprechauns, and mermaids). If a woman is going to wear a fabric that makes her sweat like a whore in church, she would much rather do it in something that shimmers. Therefore, look into lamé. As we like to say in the fabric game, “If it ain’t lamé, it’s lame.”
Really, the only thing soccer has going for it fashion-wise is the shoes, which are low-cut, ridiculously non-orthopedic, and come in an impressive variety of eye-catching colors. Hey mister, my boobs are up here! So, if you can’t do anything about the unis, sell the shoes. I mean … what woman doesn’t love to go shoe shopping?
If none of the above works, there is one last-ditch effort you might employ: Inviting women to play on your team. This is going to mean that you’re going to have to approach them and talk to them respectfully and sincerely. You might even have to sell them a bit on the benefits of physical fitness, teamwork, and camaraderie. If it feels weird, you’re probably doing it right. Here is a tip to make it less so: When you ask a woman to join your team, ask her just like you would if she were a man.