Whut?
I'm quite not getting what you're saying?
We haven't seen Kasumi for a while now (has got to be a few years in the anime). Even though Kasumi was very not into the idea of being a gym leader back then, she's probably grown up a lot more (which we have seen) and enjoys being a gym leader now.
Kasumi is tough. If she really hated that place that much, she would have found a way to leave. But she didn't, which makes me believe that she's happy there now.
First off, she would need to find another relative to give ownership to the Gym (That is, BESIDES her sisters) that would be trustworthy enough, so leaving the gym, even for her, would be too difficult to try and do (as Cerulean Gym is implied to be a Family owned gym). Secondly, she DOESN'T enjoy being a Gym Leader. I mean, as soon as her sisters took back the gym after returning from that three-month cruise, what did Misty do? She left the gym to go to Hoenn. Something similar happened in the return to Kanto arc, where she forsaked her duties as Gym Leader, and even went as far as to delay her return. That's not even taking into account her reaction in GCYL and how at least three quarters of her hosos had her complaining about the Gym.
Did Brock even try to leave HIS gym prior to Meeting Ash? He obviously didn't care for the gym, but he still went with it anyways, even when he could have easily took leave from the Gym. In fact, the first chance he had to leave the gym for good (Flint revealing himself), he took it.
Just because she's working her butt off at the Gym doesn't mean she's liking it. Take Brock, for example. He's had to work at Pewter Gym for 5 whole YEARS, and he didn't even care for it.
How the hell do you know? Again, we haven't seen Kasumi in ages now. Who are you to say that she's not doing well? She didn't want to be a gym leader at FIRST. it's been a few years now. Things change. She hasn't returned, or even showed up in Shinou. I'm sure if she wanted a break, she would have at least tried to find Satoshi and the gang during Shinou sometime.
Which makes me only think that the writers are going to have her show up when Satoshi returns to his home. And after that, she'll go back to her gym. Which is what she does.
Honestly, I find this 'argument' totally pointless, because ..in reality ..it's obvious that Kasumi is never going to travel with the main gang again. It's simple as that. Sorry to be so blunt, but :x you gotta stop lying you yourself.
Ages? it's barely even been 3 seasons/ one saga since we saw her last. That's not ages. AGES would be either a century or a millenia of seasons.
And again, you could have said the same thing about Brock's Mom making regular appearances (seeing how she was not even mentioned or seen once for 9 seasons in the main series since Brock's debut episode), yet they made her into a recurring character when they could easily not have done that.
And anyways, we CAN bring Misty back. All we have to do is convince the writers to bring her back, show them how many of her fans want her back, and they'll do it. If they could do it with Brock despite not really needing to, they can do the same with Misty.
EDIT:
Because he is semi-perverted. I never said there wasn't a semi-perverted person in the writer's block. Besides, he was probably kinda biased there.
Maybe he was only one person, but I might as well remind you that he DIRECTED the Pokemon Anime for the first 9 seasons prior to his demotion. So, as far as anyone's concerned, what he said when he was director = what all the cast and crew had said. So at least with Misty's removal and May's removal, it's true.