Flex is great to prototype.
Here’s a little thing I’ve thrown together a while ago. Pick and create football-formations.
It features a couple of custom components like a JerseyEditor, a simple Color-Picker a formation list and some custom item renders.
You can adjust the formations on the fly entering any system you like. Try 4-4-2 if you’re more in for a classical style, try 2-3-4-1 for an attacking lot or use drag and drop to adjust your own custom formation.
Clicking on a player opens up the editor so you can add your own players. And no, the colours of the jersey editor do not get passed over right now.