I'm curious what you say to people who ask "Why not Meetup?" As someone who has organized sport groups from small (single weekly pickup games in the mid west) to large (300+ people vying for spots in three games a week in a major city), I've looked into various sport-specific apps. But in the end, I've always come back to Meetup. They used to have more rough edges, but they've gotten much better. FYI, here are Meetup…
We are absolutely going to implement several of the features you mentioned, and hadn't though about some of them, so thanks again!