I really enjoyed this read and want to go on record saying that as a long time fan of the Simpsons, I absolutely and whole-heartedly endorse your proposed ending.
I can remember seeing the Simpson's on the Tracey Ullman show WAAAY back in the day -I challenge anyone to watch that clip and not want to burp at some point. Then when they got their own show it was a huge cult success. We kids looked foreword to watching the show all week long and so did our parents. We used to pop a tape in the VCR and record the shows so we could re-watch them any time we wanted. We would call friends up and invite them over to watch it with us. The Simpsons were an "event" back in the day.
I haven't watched them in years though, for a number of reasons but if I knew it was their last ever show I would definitely tune in. If the plot that you outline was what I saw, I would think to myself, "damn, I must have been missing out these past few years, that was hilarious."
Good luck, let me know if your idea picks up any momentum. There's no reason it shouldn't. Shout out @MattGroening