Improve/extend the team selector
The team selector is great but it's very basic. It would be great to be able to have more than two teams (e.g. if it's a tournament) and to be able to select formations (e.g. 4-4-2).
Pending
You could also have anonymous player ratings sent out after the game and then use this data to suggest balanced teams
Another idea could be to have an image of the teams that can be easily shared in a WhatsApp group
An obvious improvement would be to save the previous team selection so it can be easily be re-used.