You should have a smart concede function that uses a RNG to randomly concede. This could be combined with a hard limit on when to concede (say rank 19 - 2 stars). This would be a rather easy function to add in, and would make the bot look much more human, as opposed to ALWAYS conceding after hitting a certain rank. You would have to make sure it didn't randomly concede at rank 20-0 stars though, as that would also be a red flag.