Now, it's no longer that I'm really obsessed with Pinkie Pie anymore since the show has ended, but in my opinion, this is what I think the last CMC episode could have been.
After the part where Fluttershy tells the Crusaders that Twilight has her magical research project, instead of going to Twilight's castle, the Crusaders would go to Sugarcube Corner and ask Pinkie Pie if she can take them to the Appleloosa County Fair. Pinkie says yes, to the CMCs' excitement, then the rest of the episode would mostly be pretty much the same as the original, other than Pinkie Pie being the CMCs' chaperone.
I also made a comic strip out of it:
If you don't agree with this thought, that's okay, since we all have our imaginations.