The entire UI is just a couple files, it's not that hard to pull off. It's a bit more tedious than just a drag and drop but that's what I did in the first place as well, at least you won't need to do any actual graphics. A short Google will provide you with all the needed info on how to accomplish this.
As a suggestion, just enable texture saving in PPSSPP to get your own ISO's hashes and replace with my files. If the textures don't work for you then it may require you do some digging and find your correct hashes. I run the ULUS10391 ISO of the game and these texture hashes work for me.
