In my area there is a group of Instinct players that dominate the nearest 7 gyms. They're all legit and the deserve it, they put in more effort and are more organized than the other teams in the area. Good on them.

And I've found the perfect way to punish them. They are going to hold those gyms all week. Once a week I'm going to clear them out. Enjoy your 50 coins a week Instinct! If I clear them out at all.

This gym system will make gym stagnation worse not better. Why would you help the opposing team gain coins by flipping their gyms? Sure, I may not get any coins but at least neither will they. Now (unless you multiaccount) you can get absolutely nada.

I suggest to Niantic that rather than getting coins when your Pokemon returns, you gain coins as they are in the gym, passively ticking into your account. This simple change would actually motivate you to have Pokemon IN THE GYMS not returned to you.