Wendel is not really a candidate, because he hasn’t appeared on the show in years. Which pretty much points out the fallacy of the question: any character who doesn’t really work does not get much play as time wears on.
But, if you must have a Springfield JJB, and you want to pick a consistently appearing major character, I think it might have to be Maggie. She hasn’t really contributed anything to the humor for quite a while now, and I think it doesn’t really make sense anymore (even as a gag) that she never talks. It might inject a new comic element to the show if the producers started to weave into the show a more interactive (i.e. talking) Maggie. Nevertheless, this may be a bit of a reach, because there have been some funny Maggie-centric episodes, or at least parts of episodes (the one where Homer bowled a 300 game comes to mind).
The bigger problem with the show is a lack of consistency overall; the fairy tales episode was great, the Brazil episode rather lame. They need to make the show better beginning to end, rather than worry about one character.