Not on the topic of badges, but I had an idea about gym leaders.

Tristan's going to the big leagues, right? So his gym will get old old and cobwebby, and trainers won't get to go to the E4, because they can't get their 12th badge. Unless, of course, some nice fella goes on and takes his place in Portwind.

So, Portwind gym goes out of buisness for a while, and you can't go in. Then, you beat the E4 and the champion. He's all sad, but then remembers about a job offer. He goes off, redesigns the gym, and challenges you again. You can keep battling him, and he gets stronger each time. (Maybe you could get a 13th badge, while you're at it). Or he could always set up a new gym back home at Neo Bay, too.