If I remember correctly you also need an admin to look at it afterwards. An admin probably thought that the gym gave you an unfair advantage, or just didn't like the style of the new arena. I know that my gym was changed a few times in the past, but I was never quite sure to at what point was to big of a change. Though then again my gym made every new person rage quit XD. The admins should be more clear on the gym regulations though. Because I know the rules are very lenient, and in favor of the gym leader, but I don't know at what point is too much. You can try to rebuild in a different location, and have the admins approve of it, and if they do they will just replace the old one with the new one. I hope this helped.
