I checked it out at a public hotspot and it looks great, just a tad slow to load. I agree with Mottie’s suggestions. Perhaps look into a way that you can cache all the elements onto the user’s device, lets say an iPad (would be perfect for this). Then, when on the sidelines without WiFi, they can still use the application offline.
Just to reiterate, a favorites list for the user and predetermined starting layouts. It would be cool if you could save some basic formations like the Umbrella for the hockey one. This is a sweet application idea.
**EDIT: Perhaps a combination of Cache Manifest and localStorage would make the above suggestions possible.