One thing to consider might be shooting vertical sometimes instead of horizontal, especially if she's in isolation. Feels like you are wasting a lot of space on either side (especially in a shot like #3 of the first batch) and instead could get a full body shot by going vertical (which gives you a better chance to get the ball if it's closer to her feet plus seeing the whole body is also great). When I shoot someone in particular playing sports I try to spend a little time vertical and focus on getting their whole body in the shot. Takes some practice but definitely worth it.

As others have said you don't need it for sports. I shoot pro women's soccer frequently and have the first generation Canon 70-200mm f/2.8 which doesn't have IS. I never ever shoot below 1/500 (and then only if lighting is atrocious). I have zero issues with freezing motion and getting sharp photos with that lens even at night games under mediocre stadium lighting. I did try a friend's second gen of that lens at a preseason game once to see if having the IS was worth it and I didn't see any difference at all in my photos.

Even if I'm using that lens for something else unless it's pretty dark out, I can just keep the shutter speed up and shoot handheld no problem. For other stuff I use a tripod and a remote trigger or a timer delay to avoid the vibration. Let's face it, there are compromises with almost any piece of gear unless you have a ridiculously big wallet. For me it was worth saving $500 to know I can't shoot handheld in overly dark environments without a good amount of noise but would be fine any other time. I'm okay with that but YMMV.

I've been following these on Facebook and saw two issues that make me wary of buying them. First off, you won't be able to reverse your lens hood with these on so you'll need extra space in your bags to carry your hood(s) separately. Second is that it will take 2 hands to get this on and off. Simple lens covers are easy to take off and put on one-handed. The latter isn't a deal breaker for me. The former definitely is.

I shoot pro women's soccer on a field that probably has slightly better lighting than most high school football fields. I use a 7DII and the Canon 70-200 f/2.8 and have a 1.4x extender. I only add the extender for day games because losing that stop of light at night really does cause problems. I shoot manual with auto ISO and have that topped out at 6400 (I can live with that much noise). I also try not to go under 1/800 for shutter speed since the ball especially gets motion blur if I do. But I'll drop it to 1/500 if I'm at another field where the lighting isn't as good. You can probably get away with a slower shutter speed since a ball thrown is going to be slower than a ball kicked. That might buy you enough light to think about the 1.4x. I doubt you'll get away with the 2x though unless the lighting is extremely good. But as you said give it a go. But make sure it's about as dark as it will get and try shots of different areas of the field as some areas are darker than others. Good luck!

I use a 7D II and shoot professional women's soccer. The field where I shoot has good but not great lighting and I usually shoot from 6-9:30pm so I'm shooting through very changing lighting conditions. I just don't have time to mess with my settings (or even pay attention that much) while the action is going on. I missed my favorite player scoring a goal in the league semifinal last year because I was mucking with my camera. Lesson learned. These are all reasons why I shoot in manual (no slower than 1/500 but prefer faster and f/2.8) and auto ISO.

I used to not put a cap on my auto ISO but got a lot of photos with a ton of noise that were being shot at 12800. I've started capping it at 6400 and while shots are still noisy, they're acceptable to me (and I do a little noise reduction in post as well) and not too dark overall either. You just need to experiment and find what works for you. Like a lot of things in photography, you need to find the best compromise.