This is a really good question. However; sadly I won’t be changing anything to the sprite sheet in the foreseeable future. I might have a solution for you though:
What people usually do when make a jump animation is take one of the frames from the running animation. Particularly the one with the back leg is pointing downward and the front leg is pointing forward. If you freeze that frame until the peak of your jump and then switch to one of the next, you might get a pretty decent result.
Thank you for your compliment! I am happy that they could be of help in your project. 😊