It's a good idea to make these coins obtainable through only randomized battles, so that coin farming wouldn't become a thing - where players could spam on 2 computers and 2 accts. to get bunches of coins. Also. If we were to make maybe a coliseum, there would DEFINITELY have to be level guidelines. Like you could sign up for a 50s battle, which would not allow you to continue if you had pokemon lower or higher than level 50, etc. Overall, I think this is a great idea, but it would take up a lot of time, and I'd personally like to see some other things be done in the next update before something like this.
[spoiler]if the next update ever comes...[/spoiler]